Getting frustrated with the shadow dude *spoilers*

[xiphirx]

If you're in the worst situation possible (no cover, you just ran into a cell with no door) just sit in a corner, crouched and look at the wall. He shouldn't notice you. You can sneak past if you walk softly.

Most of this is avoided though, as said before, its really key to hear the sounds. You can sense that there's a monster coming literally 3 seconds before you actually see it.