This is an old bug that hasn't gotten fixed yet (it may have been lost in the bug post).Those guys in cloaks at the Temple of the Oracle (area 12).. they should be physical manifestations (actual objects you can bump into)... they are currently like ghosts (like the Specters). You can only shoot them with certain weapons (they should be able to be killed with practically any weapon anyhow).
These cloaked guys are supposed to be solid instead of "ghosts" that they are now...
Edit: This is a bug. Moderator, please move it to the Strife Bugs forum.