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1) It takes place inside a talking cave
2) The cave is mysterious. And a bit sultry>>
http://www.rockpapershotgun.com/2012/05/24/mindcraft-double-fine-debuts-the-cave/
An adventure game about a talking cave that lures people inside to explore their "dark passenger"? Hell yeah! Choose three characters of seven available and coordinate them to solve puzzles (reminds me of Trine). Some puzzles will be tailored for the unique abilities of one character, so you can't explore the entire cave in one playthrough. Each character has a unique personality and a story that will unfold by exploring the cave. The Cave acts as a narrator along side other voiced non-player characters, but the main playable ones will remain silent. Local multiplayer

http://www.youtube.com/watch?v=d6S90Q_By6w
http://thecavegame.com/screens.html