Whose blood is this?

You notice that your head is made of something like ceramic, but you don't quite know what. Immediately in front of you is a wall of glass. It seems to be rather thick. Beyond it, a white void illuminates the room. Behind you is a pitch-black corridor, and there are plain walls to your left and right. The ceiling is rather high - perhaps if you stacked around eleven of you, you could reach it.

[Look down the corridor].