I've long been considering how Sanity is handled in the Metagame universe (or "Eight Kingdoms," as I'm starting to call it).
SURELY if you gaze into the abyss, the abyss gazes back at you, right?
Right, but...haven't we seen that before? A few times? Call of Cthulhu and the World of Darkness are focused very much on retaining your sanity/sense of self/humanity in a fight against the darkness. Rippers and Tour of Darkness (two Savage Worlds settings) both tried to incorporate a sanity element into the game, neither one being successful in my opinion.
I considered for a while that perhaps channeling too much of your character would lead to them wandering around the steam tunnels under their college. Then I thought no, let's allow them to "cash in" sanity to channel, but then I realized that's just trading out Sanity for Power Points. Then I said, how about every time they gain an ability, they go a little crazier.
Finally, I said no. The game is not about a fight with sanity, really. The sanest thing to do in the Metagame is to accept the fight against the monsters. The darkness is real; the characters have a chance to do something about it; the crazy thing would be to deny all of it.
Sanity mechanics will come into play through the Fear table, which I am considering modifying, and through a checklist the GM will follow. I will probably also make the NPC Reaction Table more granular. RIght now, let's say that every item on the checklist subtracts 1 from encounter table results - which is not the same as Charisma. Finally, I will say that levels of Fatigue also subtract from NPC reactions.
Let's say your coworker Howard is a gamer. At work, you swap a couple stories about tabletop experiences, you crack the same Evil Dead jokes, and you have made a couple efforts to set Howard up with a boyfriend (NPC reaction: 10 on the table, so just this side of Friendly).
One day, you pass by Howard's cubicle and notice he's surfing eBay for firearms (GM checklist: The PC purchases a gun, so we're at 9). No biggie; in fact, you tell him that your uncle has a Smith and Wesson that needs a good home.
A month later, Howard hasn't been sleeping too well (Checklist: the PC gains a level of Fatigue from his "hobby," so now we're at 8. The Fatigue itself also subtracts one, and we'll assume Howard fails his Vigor rolls a lot to resist exhaustion - down to 7 on the table). You offer to cover for him so he can go take a nap, but you're a little annoyed that you feel you should do that.
A week after that, you tell Howard you met a guy at the game store that you think would be perfect for him. Howard tells you to go fuck yourself (No checklist entry, but the GM decides Howard's not keeping his friends these days - another -1 to the Reactions, so down to 6).
Three weeks later, Howard is putting an Ace bandage and gauze on his leg at work (GM checklist: Obvious injury, 5 on Reactions). You are getting weirded out by this guy.
Finally, one day you arrive late to work and pass by Howard's car. One window is smashed, it looks like someone keyed the hell out of one side, and you see what is obviously a pair of shotgun shells on the seat (Checklist: Signs of conflict or struggle, -1 to reactions, we're at 4 now).
Now, the thing is, that coworker NPC represents the entire workplace. With an Unfriendly result on the NPC reaction table, Howard is going to find his job in jeopardy. Howard is still completely sane (if stressed), but people look at him askance.