A Walk in the Dark A look in to the mind of an RPG designer

      

13Aug/19Off

A New Beginning

It's been eight months since I post here... better now than never.

Over the past week I've been thinking a lot, specifically about Atomic Age.

In case you don't know, Atomic Age is my post-apocalyptic treatment of the Archmage Engine, which powers 13th Age. It came to be because I wanted Gamma World, and I wasn't allowed to create Gamma World content for fear that WotC would sue me into non-existence (they had threatened to do so already). But, during its development, it became something different... It's still post-apocalyptic, but not as zany and off the wall as Gamma World is known to be. I think of it as somewhat of a cross between Gamma World, Mad Max and what the future would be like in a Terminator film that didn't time travel.

But here's the thing... when you choose a system to develop your campaign setting around, most of the time you're stuck with the nuances of that system. The Archmage Engine is a great system, don't get me wrong, but there are some aspects of it that didn't feel right or I couldn't get to work with what I wanted to do. For example, how would mutations work in a 13th Age system? What about radiation poisoning? And there are some thing that came with it that I didn't want at all... like magic item "quirks", which are good by design in a fantasy game like 13th Age but just don't fit in my campaign setting.

Since I wrote most of Atomic Age, Dungeons and Dragons 5th Edition made its appearance and the landscape changed. As is the case with the Archmage Engine, I have some issued with 5E in that, although it does some things really well, other things not so much. For example, creating monsters and encounters in 13th Age is stupid easy... in 5E, not so much. And 5E doesn't even come close to the background/icon system that Archmage provides.

So I had a crazy idea... why bind myself to a single system? DMs do it all the time... cherry pick bits and pieces from multiple systems, campaign settings, and other source material and create a virtual Frankenstein's Monster of an RPG system to use in their homebrew campaigns. Only I want to take that Monster and publish it.

So I decided to try and write my own RPG system, picking and choosing the features that I want from multiple systems and melding it all into one amorphous blob that will power Atomic Age.

I'm insane, aren't I? Seriously, I have no idea how this is going to go... mainly because it's a daunting task and I'm not exactly sure I know what I'm doing in this regard.

But I can't do it alone.

So I've done something crazy: I've reworked my Patreon to be aimed specifically towards the creation of this new engine. And I'm going to do something even crazier: try to stick to a regular schedule in which I dicuss what this engine is going to be, which means this blog will hopefully see activity it hasn't seen in ages.

Will this become a reality? Who knows... but I have to try. A lot of work has been done for the Archmage Engine version of Atomic Age, but I don't see that ever being cobbled together in such a way that I will be happy with all aspects of it. Hopefully, this way I will actually be happy with it because it'll be wrapped around something I myself put together for the specific purpose of powering the campaign setting.

I hope you all will join me on this crazy ride. My Patreon is open to your support! If you sign up now, you will get my latest published adventure, Witness Protection, absolutely free!

Ever forward...

2Feb/14Off

Atomic Age Preview: The Vorpal Rabbit

In case you aren't aware, my pet project - the post-apocalyptic treatment of 13th Age's Archmage Engine SRD - has a name now: Atomic Age. We have a website and a Twitter account, but I'm not exactly advertising yet because I don't have appropriate branding for it. I want a logo and a few creative assets before I head unto the breach that is social media.

In the meantime, development continues... Most recently on the catalog of monsters that will be included with the core book. Initially I had created the "straight", not off-the-wall monsters that could be present in a semi-realistic post-apocalyptic world - robots, soldiers, wasteland marauders, etc. - but now it's time to do the weird ones that make a post-apocalyptic game entertaining and offbeat.

While I was converting Lepus Maximus to Atomic Age, someone mentioned Monty Python and the Holy Grail. And with that the thought process was unavoidable.

Since it's actually compatible with 13th Age, here you have my latest creation: The Vorpal Rabbit. Hope you enjoy!


Rabbit, Vorpal

Normal 3rd level Wrecker Beast [RABBIT]
Initiative +7

AC 20
PD 15
MD 11
HP 44

Huge, sharp teeth +8 vs. AC - 8 damage, and the rabbit pops free from the target

Charge: The attack instead deals 12 damage on a hit if the rabbit moves first before attacking an enemy it was not engaged with at the start of its turn.
Natural 17+: 6 ongoing damage (hard save ends, 16+)

Quick footed: The rabbit gains a +5 bonus to disengage checks.

Leap about: As a move action and with a successful disengage check (if applicable), the rabbit can hop to any nearby space it can see.

Fear: While engaged with this creature, enemies that have 15 hp or fewer are dazed (–4 attack) and do not add the escalation die to their attacks.

Nastier Specials
Critical threat: When the rabbit makes a charging attack, it scores a critical hit on a 17+.

Vicious streak: When the rabbit scores a critical hit, it can move to engage another nearby target and makes a charging bite attack against it as a free action.

23Nov/13Off

On The Road (Part 2)

This is a continuation of yesterday's post in which I babble on about implementing vehicles in 13th Age.

Maneuverability and Skill, Revisited

In the three examples I provided - the motorcycle, the car and the 18-wheeler - the maneuverability and skill levels were equal, which seem to imply that there really isn't a need to define them both. So I sat down to try and decide what would represent the two extremes.

High Maneuverability, Low Skill: The Bicycle

Although I personally cannot ride a bicycle safely (due to an inner ear condition), it doesn't take a whole lot of experience to ride a bike. Heck, my son was doing it at an exceedingly early age. But someone who's very good at riding a bike can do some rather amazing things with it, if the X Games are an indicator.

Low Maneuverability, High Skill: The Forklift

Now this may sound odd, but I actually know how to drive a forklift. You would think it's easy but it actually isn't simply because it's counter-intuitive and not what you're use to because they usually steer from the back. So you pretty much drifting everywhere, and it takes some effort to get a feel for it before you go and slam into some freight.

Now think of two examples for a second... They somehow exist in your game, and the PC elects to use them somehow... Are you seriously going to do a skill check if they can? Quite frankly, if a PC wants to launch himself in to the air and do some tailwhips while he's at it are you seriously going to roll a die to see if he fails doing something that awesome? And failing to drive a forklift would probably be the single most non-heroic thing you can have a PC do ever. If anything, I'd make the drive a little entertaining and have the PC slam into a pallet or two, but I'd probably never touch a d20 to decide that.

I'm a proponent of not doing skill checks when (1) they don't matter, and (2) when they make the PCs less awesome, even with a success.

So how would this work mechanics-wise?

Skill Rating

First off, I would probably never do a skill check to operate a "low skill" transportation unless there was some mitigating circumstances. Guy decides to hop on his bike and ride off? Go ahead... Guy frantically jumps on his bike and begins to fumble the ignition while the horse-sized mutant dogs race toward him? OK, that might need a check, but I think in that case the check is more about physically turning the ignition as opposed to being able to steer the bike.

For medium skill one could assume that the PC can put the key in the ignition, but beyond that it might be a little challenging. For example, not everyone can handle driving a Mustang at 120 MPH, even on a straightaway. It's not a matter of maneuverability since you wouldn't be making any turns, it's because you're driving a car with a much bigger engine and a lot more horsepower than you might be physically capable of handling. In this case, whether you make them do a skill check or not is kind of optional and should be decided on circumstance or not.

For hard skill a skill check would definitely be necessary. I may be an experienced driver, but if you put me in the pilot seat of an airplane the best I could do is try to remember the last 15 minutes of Executive Decision ("... Landing gear!!!"). I would need a miracle from the d20 gods to be able to fly a plane.

That being said, if a skill check to determine success or failure in basic driving ability is ever decided upon it should only happen once. Your skill's not going to get worse over time; you're only going to get better. And, short of Tank beaming the training into your skull, you either know how to drive something or you don't.

So, if you think a skill check is necessary...

  • Decide whether you even need, or want, a roll.
  • Use the environmental DC 15/20/25, factoring in backgrounds and whatnot.
  • Rather than deny them the ability to drive, accept that they simply drive really, really badly.

Maneuverability Rating

Here is where it gets entertaining... Like acrobatics, doing something risky in a vehicle has its share of risks and the success depends on the driver's skill and the difficulty of the task.

For argument's sake, let's talk about three maneuvers: a 90-degree hard turn, a handbrake turn and a "bootlegger". Regardless of what kind of vehicle you're driving, each of these has its fair share of risks. Failing a 90-degree turn might not be such a bad thing, but failing a bootleg could up end you or break your steering column.

First of all, not every vehicle can do each of these. An 18-wheeler cannot physically do a bootlegger. It's just not physically possible by definition. So all you people that say "a DM should never say 'no'"... Sorry, but this one's a "no" right out.

Based on that, each maneuver should then have a minimum maneuverability in order to succeed. A 90-degree turn can be done by anyone at any time so it shouldn't require any rating. I don't know if an 18-wheeler can do a handbrake turn, at least not safely, so let's leave that requirement at a medium. A bootlegger should require nothing short of medium, so don't expect to be whipping your 18-wheeler or forklift around like that.

And then there's the difficulty of the actual maneuver. 90-degree turn, easy. A handbrake turn might take a little effort so let's say medium. A bootlegger is hard by any means.

So let's put together what we have so far.

90-Degree Turn
Maneuverability: Any
Difficulty: Low

Handbrake Turn
Maneuverability: Medium or better
Difficulty: Medium

Bootlegger
Maneuverability: Medium or better
Difficulty: High

Attempting the Maneuver

So you're behind the wheel and want to do something crazy like a handbrake turn or bootlegger. Time to pick up a d20.

First off you have to determine driver skill. If you're an average Joe, you have no skill so there's no bonus. If you're a professional driver or "wheelman", you should get a bonus, perhaps a significant one if its your own personal vehicle. Let's assume you have the Wheelman profession and are driving your own personal vehicle (or "signature vehicle", as I like to call it... For example, the Interceptor Pursuit Special is Mad Max's signature vehicle; he can do anything in that thing), so you get a +4 driving bonus.

Let's also status Jason "The Transporter, Only Less Greasy" Statham every conceivable bonus as a point of reference.

Now we have to compare the maneuver's difficulty to the vehicle's ability to maneuver. A medium vehicle should be able to do a medium maneuver without much a fuss, but a low maneuverability vehicle like a truck that could still make a maneuver (like the handbrake turn) might have some issues. So if the skill level is higher than the maneuver's difficulty, up the DC by +5 for each step.

One thing to consider is that "low" difficulty shouldn't have a DC at all and start the progression at medium. Therefore "medium" would be DC 15, "hard" would be DC 20, and "legendary" (we'll get to that later) would be DC 25.

Finally, I would think that the skill check would be Dexterity-based simply because it requires reflexes. Let's assume the PC has average Dexterity (+2 attribute bonus).

Using the environmental numbers, here is what we have:

Handbrake Turn: DC 15, DC 20 if you're in a truck
Bootlegger: DC 20, impossible if you're in a truck

Skill Check, Normal Human: +2 Dexterity
Skill Check, Experienced: +4 Wheelman (signature vehicle), +2 Dexterity = +6 total
Skill Check, Jason Statham: +4 Dexterity, +4 Wheelman (signature vehicle), +2 Engineer Affinity, +3 background = +13

An inexperienced driver has a 40% chance of success doing a handbrake turn. That feels high, but PCs are exception after all so things like that might actually be second nature despite never doing it before. A moderately experienced driver gets a 60% chance to do a handbrake turn. Jason Statham can only fail on a natural 1, which can be expected because he's that good, so much so that I wouldn't bother rolling that one. For a bootlegger, the percentages are 25% less, and Jason can succeed doing it 70% of the time which is fairly decent.

This sort of goes back to what I mentioned earlier... If you have an experienced driver behind the wheel, one that no doubt has done his fair share of handbrake turns in the past, why are you even bothering to check if he succeeds or fails? Would you dare insult Jason Statham like that? Give him the benefit of the doubt!

And what would "legendary" be? A bootlegger is pretty impressive and I give that only a "high". Now, if you try a bootlegger while getting shot at and returning fire out the driver side window, of if you actually want to try and aim while you're mid-way through the maneuver, then yeah... I might bump that up to "legendary" if you're crazy enough to try that.

TL;DR

Here are the conclusions:

  • Each vehicle will have a skill rating (which determines how easy it is to drive; checked once) and maneuverability rating (checked when you do something extreme).
  • I cases where there is no chance of failure, or there shouldn't be a failure due to sufficient experience, no roll is necessary.
  • Some sample maneuvers will be provided, just as a frame of reference. Each maneuver will have a description, minimum maneuverability, difficulty and more information if needed. I'm not going to be specific about simple maneuvers like swerving or making basic turns, but people should know what a bootlegger or a J-turn is.

And here are our latest stats, taking this all into consideration:

Vehicle:

"Interceptor" Pursuit Special
Medium automobile (1 driver, 3 passengers)
Maneuverability: Medium
Skill: Medium
AC 18     PD 16     HP 54

Maneuvers:

Handbrake Turn
A quick in place turn where you use the parking brake to slide the back end of the car around a curve, such as when "drifting".
Maneuverability: Medium or better
Difficulty: Medium

Bootlegger
A risky maneuver to completely turn a vehicle around 180-degrees while on a narrow highway.
Maneuverability: Medium or better
Difficulty: High

This post got longer than I had anticipated. Stay tuned for Part 3, where I talk about vehicle weapon mounts and, if all goes well, how to put all this into practice.

21Nov/13Off

On The Road (Part 1)

MV5BMTcxMDUyODY1OF5BMl5BanBnXkFtZTYwOTQzNDk4As part of this little project of mine, I've been trying to think of what additional rules I may need to introduce. I'm doing that rather hesitantly simply because piling on more rules go against the very nature of the 13th Age design methodology. It's made to be "rules light", or at least in such a way where the GM is free to interpret things and make his own decision.

Problem is that I'm a computer programmer and mathematics guy, so I thrive on "crunch". I like rules, or at least the availability of rules for which I can use my own judgment whether I decide to use said rules or not. This doesn't always work well at the table, of course; more often than not, players will be the ones to wheel out complex rules and try to ram them down the GM's throat. I mean, let's face it, you're never going to see a GM say "I grapple you" then reach for the D&D 3.5E chapter on grappling. Players, though, do that all the damn time, so much so that the next player to wheel out the grapple rules on me is going to get beaten to death by them.

But the thing is that a GM's job is hard enough as it is, so there's no eagerness to houserule things on the fly. Let's say the grapple rules didn't exist... if a PC says he's going to attempt a grapple, how do you resolve it? How would that work, mechanically? Can you honestly say that you'd come up with all those rules on the fly?

The Long Hard Road

One such topic is vehicles. In 13th Age, mounts and other means of transportation are hardly discussed, which is kind of surprising considering the world is several thousand miles across. In these cases the GM is expected to wing it and hope that there never comes a time when statistics on the vehicle itself is necessary, and even then they are expected to fall back to the "impromptu" table.

But in a post-apocalyptic world, where there is nothing but barren wasteland between settlements, you kind of need some sort of transportation. I keep going back to the battles in the Mad Max series of films, which are inspiring several aspects of my setting (I even have two icons - The Wanderer and The Warlord - which are loosely based on Max and Wez from Mad Max 2). I can't imagine houseruling situations like that on the fly.

But I don't want a ruleset I can beat people to death with... To put it in perspective, the D20 Modern rule book has 15 PAGES dedicated to vehicles and the rules that surround them. That's an awful lot, almost larger than the entire chapter of Combat Rules in 13th Age. No way I'm going to provide that level of detail, but I do want to provide something simplistic that has a little bit of mechanics.

So here goes nothing...

Physical Characteristics

800px-07._Mad_Max_Car_at_Silverton_Hotel,_Silverton,_NSW,_07.07.2007I do not want to describe every vehicle ever made, nor do I want to provide different details for one brand of vehicle than another. I'm not going to explicitly define BMWs as faster or Volvos as more durable... That's too over the top.

But I'd like to provide something, so I'll abstract it as much as possible.

Size: There are four basic types: small (motorcycle), medium (car), large (pick-up truck) and huge (18-wheeler). The statistics of each type multiply in the same manner as monster statistics do; the bigger it is, the more damage it can take.

In addition to its base size, we should be able to specify number of passengers. I'm not sure if we need to explicitly define what load it can carry because 13th Age doesn't have encumbrance rules in the first place, so we'll leave that out.

So let's start putting together an example...

"Interceptor" Pursuit Special
Medium automobile (1 driver, 3 passengers)

Useless Trivia: The actual car used in Mad Max 2 is in the Dezer Car Museum, right here in Miami, Florida.

Defenses: Vehicles should have a fairly low AC and a average to high PD, representative of their structure. AC doesn't necessarily reflect whether they can avoid an attack or not but rather if the shot is effective enough to cause physical damage. I mean, let's face it... if you fire a crossbow bolt at an 18-wheeler you're not likely to miss it, and if you do you should have your crossbow rights revoked.

One would think that a vehicle doesn't have MD, but I'm not so sure. In my system, in a world where there are things that don't have an organic brain, MD represents a system's resistance to digital attacks such as an electromagnetic pulse. So in vehicles that may have a high level of technology it may be conceivable that they may be shielded from EMP attacks, and this shielding is at a radically different level than what PD represents.

There will also be additional factors to these values, like a driver's ability (we'll get to that some other time), but let's leave that out of the base stats. To determine what numbers are good, I'm going to use the "baseline stats" for a 2nd level normal monster, as presented in the 13th Age core rulebook. I'll bump up the HP by 50% to represent the car as being rather tough.

AC 18
PD 16
HP 54

Now you might be thinking that that's not a whole lot of hit points for a car. Quite frankly, it doesn't take a whole lot to disable a car in a first place; this isn't a tank. It'll take more than a PC would, sure, but it shouldn't be anything astronomical. And although one could argue that certain weapons won't do much to a car it does have its weak points; a dagger might not do much more besides scratch the paint, but hitting the tires is a whole other matter.

Vehicle Rating: Pretty much anyone in a post-apocalyptic world can drive a car. The question is whether they can drive a car well. And although most people can drive a car, driving an 18-wheeler takes a whole different skill set most people don't have.

Furthermore, there are certain things that a vehicle won't do no matter how good a driver you may be. I don't care if you're Jason Statham, you're not going to do a bootlegger in an 18-wheeler no matter how hard you try. Well... you can try, but it won't end well.

But that's the thing: I don't want a GM to tell a player "you can't drive that." I think every player should be able to drive everything... sometimes it might be super effective, sometimes it might border on comedic. If you're in a crisis situation, where you hop in to the nearest truck to flee the gang of marauders chasing you down, you'll find a way to drive the thing. Sure, you might strip all the gears, but it would be extremely anti-climactic for the marauders to pull you from the driver's seat and beat you to death because you couldn't get the truck into first gear.

So the mere act of driving shouldn't require a skill check, or at least leave the GM the option to call for a skill check only in extreme situations. In these cases, he should only call for a skill check if the story has a way to go on a failure; in the above example, failure is most likely death if you think about it, so if you're not ready to change the story for dramatic effect then you shouldn't require a roll and present the possibility of catastrophic failure.

So the way I see it there should be two separate ratings:

Maneuverability: This defines what the vehicle might actually be able to do. Should be as simple as "low", "medium" or "high" and be mapped to the environmental DCs (25/20/15 at Adventurer Tier). They should only be used in cases where there is the possibility of failure.

Skill: This defines what it takes to drive the vehicle effectively under what would be adverse conditions. For example, if you're driving a bus you can let go of the wheel now and then without an immediate end to forward movement because the thing continues to lumber down the road. If you're driving a motorcycle, you better be damn good at driving it before you even think about letting go of the bars.

Let's pretend your Sandra Bullock. You have to make hard 90-degree right turn or things will get really, really bad. There are three possible vehicles you could be driving:

Motorcycle (high maneuverability, high skill): You probably can't drive the thing right in the first place. Although it is designed to be able to make the turn fairly easily, you might not know how to handle it through the turn without having the tires slip out from under you and send you sailing off the side of the road.

Car (medium maneuverability, medium skill): Most people can make this turn, even at high speed. Heck, I *have* done such a turn myself, and I admit I am far from the best driver in the world.

Bus (low maneuverability, low skill): It doesn't take a rocket surgeon to drive a bus, but nothing short of an act from Keanu Reeves God will get you around that turn without slamming into the retaining wall.

So what does this mean mechanically? Well a skill check may or may not have been made in order to get this far in the first place; if Sandra was trying to drive a motorcycle at high speed she probably wouldn't have gotten three blocks before getting sprawled across the pavement.

Let's say she's driving the school bus. The DC for making such a turn should be extremely difficult for a lumbering behemoth like a bus, say a Dexterity DC 25 check. She's not skilled and has no additional benefits (no Wheelman profession, no engineer's Equipment Affinity: Vehicles). Maybe Keanu can give her a circumstance bonus, but that's about it.

Now let's say she was driving a car, has the Wheelman profession and some sort of background to further back it. The DC for medium maneuverability should be a base Dexterity DC 20, but she'd have her fair share of bonuses (assuming it's her own "signature" vehicle she gets +4 for Wheelman, plus let's say an additional +2 for background). Given more than average Dexterity (let's say a +2 attribute bonus), that means she totals at about a +8. At a DC 20, that gives her a 40% chance of making the turn. There may be some room for additional bonuses here and there (I still need to do some balancing of all this), but you get the idea; that's actually possible and, given the difficulty of such a maneuver, fairly reasonable.

If she was driving reasonably slowly, any idiot can make a turn like that. Even if she was driving at an average speed, given that she has the Wheelman profession the GM could argue that she would still be able to make the turn relatively effortlessly, so unless he's just dying for a natural 1 there wouldn't be much a need for a roll then either.

So let's add to our example:

Maneuverability: Medium
Skill: Medium

To Be Continued...

In the next installment, I'll get in to some more vehicle options I'm considering and how to translate all of this into something manageable within the Archmage Engine.

12Nov/13Off

One Unique Mutant

So in light of my last post regarding mutations, I've been doing some thinking.

A Step Back

Before I proceed with the full on development of this project, I had to stop and think of what exactly my goals are. I have a general vision, and I have the game mechanics to do it, but what exactly is the expectation? This whole idea popped in to my head because I was denied creating content for the-system-that-shall-remain-nameless... but is that really what I want? Is that really what everyone wants?

The thing with all the other systems is that they are significantly more complex mechanically than 13th Age was designed to be. Like I mentioned in the past post, I don't want to create a game based on the Archmage Engine that includes a new "feature" that consists of several dozen rather large tables, because that defeats the purpose and turns the system in to something it was never meant to be.

But I want what the-system-that-shall-remain-nameless brought to the table: diversity. You can be anything you wanted to be, and you can either play it serious or be as off-the-wall zany as you want to be. Want to play the hardened veteran driving his Interceptor, dog at his hide, down a barren road to nowhere? Yes, you can absolutely do that. Want to be a mutated chicken with an Uzi and a jetpack? A sentient gorilla that throws explosive coconuts and can call lightning? A giant tulip with a broadsword that can breathe fire? Maybe we can do that too.

So my goal is simple: I want to create a system that provides all these options, but doesn't overburden the game with thousands of new rules and tables in order to do so.

Balance

In doing my research of other post-apocalyptic systems, and reading through the lists of 100+ mutations some of them provide, I came to realize something: they are imbalanced as hell. While some mutations might be mundane or mechanically insignificant, others have paragraphs of mechanics and could end up being far too powerful. Skewing the balance too far in either direction makes it really difficult for the DM, mainly because every encounter and event is more or less balanced and based on the fact that each and every PC is more or less the same.

Let's take an example from D&D 4th Edition: horns. Tieflings and minotaurs both have horns, but while the tiefling's horns are just cosmetic the minotaur's horns are significantly beefier. Therefore, they have mechanics defined for them: all minotaurs have a gore attack as a racial power. But in order to be able to use those horns for a mechanic effect they have to give something up, so the gore attack is all they get at the race level. Tieflings have a different, not-horn-based racial power they can use, but giving a minotaur a gore attack and something else will suddenly unbalance the system.

Levels of Mutation

So before we decide what cost a powerful mutation will have, we have to define what they are.

For further discussion, let's use an example...

Example: Tom, a player, decides his PC is going to have a mutation that gives him wings because he wants to everyone to think he's some sort of demon and he wants to be an all around badass.

The way I see it, there are three possibilities:

Cosmetic

A cosmetic mutation has zero mechanical effect. It has no impact on the game mechanic at all. Players and PCs alike may choose to use it like they would a background or a "unique thing", but it should be under very specific circumstances and not all that often.

Example: Tom's PC has thin, frail wings that are incapable of flight. He uses them only to make everyone think he's a demon, but he's not very good at it. While having social interactions with NPCs he may try to use them to appear intimidating, but the wings are frail enough that he's not all that convincing.

For things of this nature, there really isn't a need to take anything away. As far as I care, so long as you don't abuse them functionally you can have as many cosmetic mutations as you like (within the limits of how many mutations you can physically have; we'll get to that some other time). So if you want to be a six foot tall rabbit with wings, a forked tongue, a unicorn horn and a tail... so long as none of those has a mechanical impact and are "for presentation purposes only", by all means knock yourself out.

Low Impact

The mutation has a modest mechanical effect, but it is only applicable in very specific circumstances and even then is not all that dramatic.

Example: Tom's PC has wings that he still can't use to fly, but they are beefy enough that he can use them to appear intimidating and be convincing. He can also use them to make a controlled landing when he falls from high altitude, similar to a wizard's feather fall spell, but doing so can be somewhat painful as it puts a lot of stress on his wings.

This category is the hardest to manage, at least in terms of a DM. It crosses a fairly thin line between "insignificant" and "major", and would be up to both PC and DM to decide how the mechanics are going to play out. This type of mutation should only have one, maybe two, special cases in which it can be used; any more and it stops being "low impact" and graduates to being "high impact."

I don't think this merits taking anything away from the PC besides limiting how often they can use the ability. For example, the ability for the wings to arrest a fall should be limited to once a day because of the stress it places on the wings. As a DM, I'd be very careful that something initially defined as "low impact" starts getting abused. Worst case, it gets promoted to "high impact" and has an associated cost.

High Impact

The mutation has a major impact on everything the player does, and pretty much has to be taken in to consideration regardless of what they may be doing.

Example: Tom's PC has wings that would make dragons jealous. He wants to be able to fly at altitude, use them to block incoming attacks, use them to make attacks and be an overall demonic badass that makes everyone cower in fear.

I sometimes hate players like this, but that's a separate topic.

Being able to fly, especially at altitude, is what many will call a "game changer". It significantly alters the tactics of any fight, and could be abused more than you can imagine. D&D 4th Edition restricts flight significantly for that very reason; pixies, human-shaped insects that should be able to fly wherever the hell they want, are denied high altitude flight for that reason. Letting them continually get out of range and fly circles around their opponents grossly tilts the balance scale in their favor.

This is the sort of thing that either has to be documented fairly rigidly or agreed upon in full by the DM and players, and a mutual agreement has to be made to ensure that the rules are not only worth the cost (we'll get to that later) but don't break everything the DM has planned.

For example, some of the possibilities on how wings of this nature can be used and how they may translate to mechanics:

  • Tom's PC can look intimidating as all hell when he spreads his massive wings. This can provide a bonus to skill checks in social interactions, similar to backgrounds.
  • Tom's PC can wrap the wings around his body forming a shield. This would require a standard action and would grant him a +1 bonus to AC and PD until the start of his next turn.
  • Tom's PC can fly, but he will get fatigued easily. If he takes off and ends his turn at altitude, he is weakened (save ends). If he is at high altitude or been aloft for long, it becomes a hard save (16+). If he fails a save, he falls.
  • Tom's PC can use his wings to perform a wing beat attack (Target: all engaged opponents, Attack: Highest attribute + level vs AC, Hit: Level x d6 + Strength mod damage, Miss: Level damage). He can only do this once per battle.

Needless to say, these are some serious mechanical advantages. But, after mutual discussion, they actually sound cool when you think about it! And I'm always an advocate of doing cool stuff at the table, so it wouldn't take much to convince me to use these rules... but there has to be a cost. So to get all of that, or maybe part of it, it'll cost you a feat. And the advanced abilities of the wings (such as flight or wing beat) may cost you a second feat at Champion Tier.

Conclusion

Given all that, here's what I'm thinking.

  • You can have as many cosmetic mutations as your body will bear, without any cost besides physical and biological stress (we'll cover that another time). I will probably document some examples, but I don't know if I will document 100+ possible mutations. Maybe in a supplement...
  • Several "high impact" mutations, at least the most common ones that I can think of (wings, cybernetic limbs, tough skin, etc...) will be documented. Some of those mutations will also have secondary and tertiary feats associated with them, all with a mechanical effect. A PC can take one of these mutations in place of a feat, and the mutation will have a mechanical effect more or less parallel to what a feat of the same tier would.
  • Provide guidelines on how PCs and DMs can work together to flesh some of these ideas out, specifically the "low impact" options that tread the middle ground. I might provide some basic examples of "low impact" options as well, but won't spend too much time on them.

So do you have any ideas?