The setting is in the works, but it's a simple fantasy/medievalesque world. Humans only.
Handily, the protagonists have standard "Hollywood" amnesia: incapable of remembering a thing, save their simple motor and linguistic functions.
Of course, to spice up what sounds quite simple and boring?
Each player prepares a character down to their likes, dislikes, eye colour, whatever... EXCEPT the backstory and memories.
The background and skillset of the character? Are written by another player, so the character's player doesn't know the backstory and past of their character.
(I don't think I explained that clearly enough, I'll probably clarify this at a later date)
Apart from that, this will be a very, VERY rules-light (meaning none to speak of) dungeon romp.