Portal 2 brought us everything we loved about the first game (portals) and left out everything we hated (cake-related meme horseshit). What it also brought us is a whole bunch of weird secrets, and some of them are downright creepy.
Who knew a game about ripping holes in reality could get creepy?
For instance, in one of the earlier test chambers of the game, you can find an abandoned room hidden off to the side of the level, much like the abandoned rooms found in the original game. This one's got a creepy surprise, though. If you stand close enough to one of the graffiti-covered walls, you can hear a kind of disturbed chanting. Someone went ahead and pulled out the sound files embedded in the game: the voice is clearer, but still nonsensical.