I was messing around on the level 'Regret' tonight when I came across what appears to be a sewn together doll of a Prophet. I found it on the far side of the second level of the trio of tower clusters in the main lake. It's the one you can't get to unless you grenade jump there.

This way be something I'm just out of the loop on, but I thought it was neat. It didn't seem to be tied to an achievement (at least none popped up for me) and I was OK to approach it, but any attempt to touch it, kneel on it, melee it, etc and it vanished. Not sure what that's about. Here a pic I took: