I thought about something like this:
You have a very big map,huge.
The humans have some certain goal,that only they know.
The monsters role is to patrol the place and kill the humans.
There are 4 players,two humans and two monsters.
Players humans can communicate by basic set of words and phrases through sound built into the game.
(if you prees '1',player say "Let's Split", if you prees 4 player say "Help Me!".)
Monsters can't communicate,they just can make scary voices and growls.
The humans are running faster than the monsters,so monsters must caught them by suprise or in close places.
Only monsters can attack,but humans can set traps to slow them down and run away.
For humans,monsters are invisible in the darkness. Monsters have long-range night vision.
Sound pretty good to me
(Oh and sorry if i had any english mistakes,i don't speak english
)