Multiplayer/Co-Op & Frictional Games? NO!!!

[Kreekakon]

-You can betray your friend to save yourself: survival is human instinct, and sometimes when we get desperate, we do things we would never even think of doing to save ourselves.
-You can bait your friend so that a monster would attack them before you. Whether this would be done by
sneaking meat into their pocket, or making them smell a certain way by dumping bile on them, I don't know.
-You can push your friend to make them stumble, and possibly fall.
-You can lock the door behind you with them in the room if you don't want to risk a monster getting you.

A problem with this though is that it would probably piss your friend off very much if you just backstabbed them, and if either of you are familiar with the system, neither of you would be very much emotionally affected by the sacrifice, as its for gameplay progression reasons.

I believe The Thing game had something like that, but I haven't actually played it so I don't know how/if it worked.

I've played the thing, and I have to tell you although the system is there, it doesn't really impact gameplay that much. You're much better off milking every NPC's "support fire" as much you can, than using a blood test on them to expose them. If you expose them, you have to kill them, and you lose a gunner, as opposed to just letting them come with you, and continue helping you until the very last second when the thing decides to try to transform, and jump you.

Also, the system is also a bit flawed in the fact that EVERYONE eventually will become a thing.