OK, well, I'm considering writing a short RPG in which dreams have begun to translate themselves into physical manifestations.  I'm thinking about using a PDQ-style system to allow players to create extremely free-form characters.  Now, in the game killing an opponent gives you points toward another dream attribute, most of which are monstrous/bizzare.  After you gain a certain number of points, you are compelled to take another attribute.
  This means that players can advance very rapidly in power and skills by killing opponents.  However, once you gain a certain number of dream attributes, you leave behind the physical world and your humanity, becoming just another dream-beast.  There is a drug which can sever you from the dreamworld, but it is very rare and expensive.
  Also, because of the nature of the setting, it will no doubt be necessary to kill creatures at some points.
  Overall, this means games will be on a time budget, for inevitably every character will become a dream-beast, no matter what.  Do you think there's an interest/market for this kind of short, limited-time game, or that it should be tweaked to be a little more "traditional?"

So what do characters do in this game? Kill stuff to gain more dream abilities?

I would like to hear more about your setting, and what your specific design goals are. From there, I think we could more accurately judge whether or not people would be interested. One question you might ask yourself is: Why would people want to play this?

Along those lines, what are YOUR goals for this game? Do you want to sell it? Is it just for you and your friends?

You can check Don't Rest Your Head, perhaps that's what you are looking for. As for short rpgs there are plenty, so I don't think such mechanic should be tweaked into more traditional rpgs. Anyway, a mechanic where characters can earn varied powers each time they kill an enemy wouldn't stand a long campaign unless it gets tweaked too much. Perhaps if they can keep each power for a limited time of uses, it will becam more important to keep killing monsters; and then again, if they kill too many monsters they became one themselves since they can't control all their powers. Well, hope this helps.

The trajectory of PCs sounds a bit like Call of Cthulhu: if you tap into this well of eldritch power, you eventually go crazy and die.
But then again, given that characters must go forward unto madness (how's THAT for a sub-title?), it's like a conversation in Who Framed Roger Rabbit:

Eddie Valiant: "Drink the drink!"
Roger Rabbit: "But I don't want the drink!"
EV: "You do!"
RR: "I don't!"
EV: "You do!"
RR: "I don't!"
EV: "... you don't."
RR: "I do!"
EV: "You don't!"
RR: "I do!"
EV: "You don't!" *hiding a grin*
RR: "I do! Listen to me: when I say I do, that means I do!" *drinks the drink, cue freak-out*

Thanks for indulging me on that; what I mean is, there's a clear trajectory laid out for the characters, and, Polaris-esque, you can only bob in place, not actually fight the current. Or can you? Also: I think becoming a dream-beast sounds like a sweet deal! Could a PC-turned-dream-beast get "eaten" by another PC who hasn't turned yet?
That'd be hot. I'm envisioning a sort of gauzy mist or haze pouring forth out of the rapidly-disintegrating dream-beast our heroes have just slain. As they catch their breath, the mist soaks into their lungs, and it feels good.

  Well, I have a couple of ideas, but I think this game would be focused more on really short adventures.  I think the strength would not necessarilly lie in the mechanics but in constantly balancing survival and humanity.  As I think about it, I think that the way to go might be in ratcheting up that tension and constantly making you feel like your about to topple over into one extreme.
  Also, maybe there could also be more than just survival on the line.  Maybe you have to protect or provide for a community, so you don't just have your own life on the line.

You could go in the direction like Drowning and Falling... PCs are expected to die, so everyone has a couple ready. You could even plan the downfall of certain PCs in order to cue the entrance of a new character...

"I last communicated with my brother by phone a few weeks ago. He spoke to me in hushed tones, as if afraid that someone... or something would hear him if he spoke too loudly. He said they were chasing him, and that no hiding place could allow him to escape their dreadful attention. His ramblings became incoherent before he slammed the phone down. My brother has never displayed fear in all the years I have known him, he was too logical, too intelligent... Whatever it was, it had to be dead-serious. And so here I am in London, investigating his disappearance amidst the rain and darkness in a city pervaded by a deep sense of unwelcome..."

  I think I'm going more toward "the PC's are expected to die/transform into monsters approach."  Just today I thought it would be cool if players whose characters transform into monsters could create new characters and try to redeem themselves or continue playing the monsters.  This could give the game a really great versus aspect, since players would be really worried about characters who are nearing transforming into monsters.  Do they kill them?  Try to help them?
  Setting-wise, the game occurs in our world after people start transforming into monsters.  Players are those who can (at least for a little while) walk the line between the monsters and the cowering peasants who refuse to use their powers. 
  I think for the system I'll shoot for a PDQ-esque freeform system, except with more intention hard-coded into the rules.  I think the rules should just naturally create the kind of story I've described above. 
  Basically, players create a certain amount of Traits (think Qualities) for their character.  Each trait has a different class.  For example, Skill or Power.  In PDQ, one of my problems was the fairly unrealistic damage system.  A taunt does as much damage as a sword wound.  While that's great for swashbuckling style, for this game you apply Attributes to each Trait, for example, Terrifying or Cutting, that determine what kind of damage/effect they cause.
  With Attributes, that'll also give a little room for some interplay between powers, like RPS on a much subtler scale.
  Also, the GM is able to pick how many Dream Powers the characters get, depending on what kind of game he wants to run.  He could start the characters off with the minimum amount, or concievably have them start off where 1 more Power causes them to lose their humanity.
  Maybe their could also be "eras" to play in.  For example, you could start when the Dream Powers are just starting to manifest, and maybe the players are part of a handful that possess them, or maybe go all the way to the post-apocalyptic stage right away, or start at the beginning and go all the way to the end.
 
  I definently don't want this game just for my gaming group, but at the same time I don't want to go totally "professional" with it, either.  Maybe I could release it as a cheap pdf or something.
  Any way I go, though, my goal with this is to create a small, very freeform ruleswise but tightly-focused theme and story-wise game that creates stories of desperation and ocassional hope.  The key will be keeping it packed tight, but giving enough fiction, good writing, and rules to let the players run with it in the right direction.
  Keep the comments coming, especially on my rules ideas, because the sooner I really have a clear outline of the rules I'll be able to start on Draft Zero.

noahtrammell wrote: This means that players can advance very rapidly in power and skills by killing opponents.  However, once you gain a certain number of dream attributes, you leave behind the physical world and your humanity, becoming just another dream-beast.  There is a drug which can sever you from the dreamworld, but it is very rare and expensive.

  Good point.  On setting, I'm not sure if the whole "dream" concept works anymore.  I think it would be better if it were unidentified, since that would give players a bit of freedom in finding out the secrets of the world.  I think the powers are going to have a little more gruesome aspect to them than I was first envisioning.  Think the difference between Wolverine before he got his claws coated in adamantium and, say, Cyclops.

  Also, as a reply to the "mist pouring out of the dream beast," one of the mechanics is going to be that Dream Points (I'm going to keep using Dream until I come up with a better name) are divided between the people who killed the beast, meaning that teamwork is encouraged if you're trying to stave off the inevitable.  Maybe "eating the monster" will take on a little more literal meaning.  You have to get a the thing's essence somehow.

  Here's two examples of how the game could play:

  Josh held on to the gun as tight as he could, afraid that the sweat pouring from his palms might cause him to lose his grip.  He was running through a circus, pumping legs carrying him down narrow alleys and around blind corners.  Beside him, Len and Rocky were pushing themselves to the edge as they fled whatever it was that was chasing them.  At last, Josh stopped in the shadow of a circus tent.  He listened hard, but heard nothing but the slap of tent cloth and the far-off wail of a calliope.  Everyone needed a little rest.  Bad idea.  He felt a heat on the back of his neck and his nostrils caught the faint scent of brimstone.  He drew in his breath to scream, but Len beat him to it as something swept him from Josh's side and tore through the tent.  The scream stopped, and the sounds of devouring began.  Josh fired two shots blindly into the tent as his scream finally made it out of his mouth.  "Run!"  He started  to move, pushing down the temptation to reach into the back of his mind and let It out.  Come on, surely the thing would leave you alone if it saw the bony tusks rip through your chest.  Its claws couldn't get through that kind of armor, and then you could hit it back, get revenge for Len and Jerry and Sol.  Just for five minutes.  No!  Josh focused on the pain in his legs, losing himself in the rhythm of flight as he pounded down the alley toward the light and, hopefully, safety.

  Or, Josh could activate his power, rip the thing apart, and double his strength.  Maybe Len could've made it if he'd been using his power.  Either way, I don't think they'll last long.

  Right now I'm just posting a bunch of random ideas and examples, just to give you an idea of my constantly-evolving vision for the game.  Don't think you need to read everything, but keep making suggestions or critiques about how the initial high-level mechanics jive with the actual examples.

I've always liked the idea of characters having powers that are risky to use.
I'm imagining a darker, more violent version of the Persona series for some reason. =)

Some things that might give play more meaning:

If you're already going for a tragedy (PCs inevitably die), why not ask the players how far along each of them should be, and at what point it's set? Players will pretty much do what you tell them to, unless they really hate it, so giving them the option is a good step in letting them find their creative voices (instead of just listening to the GM's).

As far as nixing the Dream idea, "Dream Beast" is a sweet name. I have to say, though, on that note, getting X-Men style powers seems like kind of a cop-out, not the least of which because it's an idea from, you know, X-Men, instead of your idea. If you have plans for the proposed setting to affect the whole planet, you've got some time for this thing to shake out - crazy mist-bleeding monsters that pop out of the shadows, wearing the faces of your friends... what a way to live! Given the descriptions you've shared so far, it sounds related to some kind of id-realm or chaos-dimension or something, or maybe the creepy "L-Space" from 2000AD comics like Slaine.

I dunno; I'd much rather find out I could turn my whole body to mist and "skate" through the air, or grow fearsome talons and wicked musculature and so on. That sounds like what you're describing in the "circus scene", Noah.

Finally, I think that a player should absolutely be able to lock himself out of transformation, or at least aspire to that (and fail?) - one thing that Peter Parker could have always done (but chose not to) was to retire from crime fighting because it wasn't worth the personal cost anymore. From a marketing perspective, that'd be dumb, but if he were, say, part of a team, it wouldn't have crippled the narrative quite so much. But even then, the comic wouldn't have to stop - the writers could up the ante pretty easily by saying "ok, now there's no Spiderman, so X,Y, and Z happen. How does Peter react?" Moving away from the Spiderman analogy... if you want good-faith protagonism available to the players, then they need to be able to make any choice they can think of in response to the game's premise, and the system needs to be prepared for that.

It's absolutely a danger that the game might not account for any possible decision - in my Mask of the Emperor playtest, a game about honor and reputation and a godlike Emperor whose powers make public opinion very, very tangible, my players decided they didn't give a fig about honor, and wanted to bring down the system. They weren't interested in building a name for themselves or letting their identities be known; as a result, 50% of the rules went untouched for the whole storyline. I'm realizing that I should have done something to put that decision "on the map" - belatedly, I figured I could minimize the stats of anybody who's an Unknown, while only giving above-average abilities and beyond to those who are Known to His Holiness, the Godlike Emperor. Hey, I think I just reinvented my game! Awesome :) Anyway, pretty much any GM-advice-guide, be it Forge-y, mainstream, or whatever, is going to tell you that players do unexpected things. Leave room for as many answers to the Premise as possible, and the game is less likely to break.

  This is all good food for thought.  From what I've heard of Persona, that's probably a fairly good description.  I think the thing to imagine when trying to get an idea of the powers in the game are fishgills and roadkill.  Healing characters don't use telekinesis to bind up your wounds, they have leech-like openings on their palms that they use to pump an adrenaline-serum cocktail into your bloodstream, or poison.
  I like the idea of having a bit more freeform style, but I think the mechanics as I envision them are really going to enforce a certain downward-spiralling direction.  Since so far one of my points has been keeping the game focused, maybe I should come up with a more coherent setting, so that all the players are protecting a community of "regulars (that is, people who refuse to use their power at all)" or just trying to survive.  The idea with the mechanics is that you always have the choice to not use your powers, it's just that the decision to ignore your ability to have claws burst from your hands will be really hard to make when you're facing down a ten-foot-tall thing that looks like a T-Rex turned inside out. 
  I agree that Dream-beast is an awesome name.

  This has made me think a lot.  I think now I'll just keep on discussing this, but I'm starting work on an overview of the world.  I'll post it when it's finished so everyone can really get a good idea of what I'm going for.  There may be some mechanical stuff in there, but it'll probably be more of a narrative-style intro.  Man, in no time at all this idea has really started to evolve!

Abkajud wrote: ... if you want good-faith protagonism available to the players, then they need to be able to make any choice they can think of in response to the game's premise, and the system needs to be prepared for that.

  I think mechanically you'll be able to play a non-Dream-user (though that won't necessarilly make you good), it'll just be a heckuva lot harder to survive when you have a pistol instead of fire control to fight your enemies.  But those are the kinda choices your going to have to make, and I think that's kind of what I want to the game to be about: balancing survival and the beast within.

Noclue,
I agree with you about Dogs. Where I don't agree is this: in relation to the Premise of a game, players need to be able to make any and all choices they wish. By Premise I mean the big one, the moral-ethical question that the game asks the group to answer, or at least discuss, through play. Given the Forge definition of Premise, then, it's imperative that, with regard to dream-beasts, transformation, etc., players need the freedom to do whatever they want in relation to the power they could gain from huffing dream-fog.
See what I mean?
Noah, it sounds like we're on exactly the same page. -grin-

  I was considering the actual rules of my game today, and I might add a "Despair" system.  It basically arose from the fact that social skills really have no use if all you're trying to do is survive.  Despair is basically like damage, except that it doesn't just influence, say, physical rolls.  It also branches off into mental and focus rolls and should be roleplayed, too.  However, Traits can purchase Attributes like "Inspiring," and can then be used to dispel Despair.  This'll make things like eloquence or music important because without them, the only way to overcome those penalties will be to use your Powers.  I'll have to come up with guidelines of when Despair comes into play.  Maybe when partymembers die/lose their humanity, that way you'll be depressed and have a monster on your tail.
  Man, I feel sorry for my players.  They may have freedom, Abkajus, but going the "good guy" route is not going to be easy.

Noah,
You might want to check out Polaris for an example of how to do this Despair idea without railroading players, in the manner of Vampire's Humanity system or Call of Cthulhu's Sanity score. Maybe Despair gives players more power, but power that can only be used in certain, antisocial ways?

  Well, I was considering that Despair just accumulates as your situation worsens.  However, today I came up with the idea of a Coping system, where your player has a psychological disorder they use to cope.  If you were anorexic, you could take a Hunger status to remove Despair, but that would come back to bite you later.  As with everything else in the game, you're staving off your inevitable doom.
  However, I'll check out Polaris.  I've heard a lot of good things about it, and I don't want the only option for staying happy to be harming yourself :)

  Actually, could you just give me a quick synopsis of how it works?  I'm leaving town in a couple of days for three weeks, and I don't think I'm going to have time to pick up a copy.

  Also, from a combat standpoint, I was trying to think of a way to make Powers much more, um, powerful than Skills.  Since I'm still kinda using PDQ as my inspiration, the difference is that Powers can be used to absorb damage while Skills can't.  While you can still hit an enemy if you have a really high Guns skill, he'll be able to take the hit on one of his Powers, but you can't absorb it with your Guns skill.  In this way, Powers are a combination of Skill and Absorption Traits.

  OK, so I think this game has evolved enough to warrant a place where I can compile my development notes and random stuff I come up with.  I've written a short introduction to the game, and I think I'm going to name it Outbreak.  I hope the short fiction piece I've just published will help everyone to get a clear idea of what the game is about.
  For those who are interested in following the game, the blog is located<a href="http://www.untrammelled.wordpress.com/">
here.  I think I'll just keep discussing the game here at the Forge, and may create new threads to discuss certain questions.  I'll use the blog to keep all my notes organized, so if you want more miscellaneous info, the blog will be the place to look.  If you want to, I can make anyone who asks a contributor on the blog (you'll need a Wordpress account) so you can comment on the posts, but it may just be easier to discuss stuff here. 
  I hope everyone keeps following and critiquing the game.  Everyone's input has really helped the basic concept grow into something I couldn't have created in a vacuum.  I'm leaving for three weeks this Sunday, but I plan on continuing writing, and for two of the weeks I'll have access to a computer that I can use to post anymore progress I make on the blog, or create new threads here at the Forge.  Thanks again!

-Noah