So basically, trying to put it all together (for me anyways):
Gloomweaver: On the front side, he/she/it/whatever has just gotten into this world (the art depicts him just getting off a table, presumably the one he was summoned on), and the 'skin' he is using is still an immature shell/cocoon. At this point, he is feeding on death, maturing, growing stronger (as Spiff said, he gets stronger with every death, and he preys on the weak.). Unfortunately for him, the heroes come along and attack him, and the shell starts to break (apparently, the shell has 50HP worth of durability), letting out his "true essence", which I assume is highly unstable because it does not belong in this dimension. Gloomy needs his shell; without it, he starts to rot (hence, rotting god). In a desperate effort to stay around, he starts attacking everything indiscriminately, even feeding on his followers. All the while, that massive true essence of Gloomweaver (worth, apparently, 100HP, which kind of makes sense since he's a god and all) is deteriorating, which explains him attacking all targets, even himself.
Which makes me think: if/when the heroes finally defeat him, here on this plane, with his essence stuck here rotting, does Gloomy cease to exist? Or does he slip back to his own dimension, as these things tend to go? Actually, by the time the heroes break Gloomy's "shell", he loses-he's going to end up consuming the world wildly, trying to stave off the rot, but eventually he will run out and perish. The flip side fight is basically just the heroes trying to contain the Gloomweaver threat, i.e. not letting him consume the world, but essentially, the moment the shell is broken, Gloomy is screwed. I think the best line here, as provided by phantaskippy, is: "This is a gamble gone wrong, and the heroes are facing the last acts of a dying god." (lol sorry, I'm not tech-gifted. Not sure how to block quote it. Hehe.)
Spite: Spite is revived by Gloomweaver to cause death and destruction and gloom (?). The drug cards represent the various powers that slowly become available to Spite as he kills more and more people, blessings as it were from the evil god. However, as the heroes save more and more people (and more importantly, deny him his kills), he loses Gloomy's favor, and so he loses the unholy forces holding his body together, resulting in his Broken Vessel side, at which point he goes berserk. He gets wilder for every victim that eludes him thanks to the efforts of the heroes (+1 damage), and whenever he destroys a victim, he gives an animalistic howl of triumph, disheartening and harming the heroes. On the safehouse/victim side, getting them in the safehouse allows the heroes to draw a card, representing (maybe?) the tiny hint of satisfaction and accomplishment they get for saving people. Alternatively, letting them out of the safehouse to 'run for it' frees them up from having to guard an additional person, allowing them to do more things (play a card).
There are some alternatives. As Matchstickman shared (and actually, I am more inclined towards this explanation), Spite was resurrected by Gloom and made into a sort of self-perpetuating machine (I am not sure this is the best term, but whatever. I hope you get the gist.): a killing machine that stays together by killing more people. The more he kills, the greater his own power becomes, and the more saved by the hero, the less able he is to hold his own body together, leading to the Broken Vessel. Through it all, Gloomy benefits from the general atmosphere of dread and evil and whatnot generated by his pawn. (I prefer this over the theory where Gloomweaver withdraws his support/blessings because Gloomy never struck me as the micromanaging type-I seriously doubt that he would care enough to pay attention to what his agents are doing exactly. Much more likely that he'd just leave his agents to their own devices.)
Which leads to this: if the heroes win, then the Vessel is destroyed and Spite goes back to the grave. Simple enough. But what happens if Spite wins? Is he doomed? Or does he, through the malevolent energy that seems to be produced by killing people, return to his old, unbroken body to continue killing for th glory of Gloom?
Mind you, I do not claim that this is correct. Just trying to put together some of the points that seem to make sense to me, from this thread, from the oversized Villain cards from Spiff's site (Thanks so much Spiff! You rock!), and some of my own thoughts. I'd love an *official* response though.
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As a side bar, why does Gloomweaver want to break into this world so badly anyway?
My guess: Nachos. The Realms of Discord probably has crappy nachos.
