Turn Undead (in theory) causes all undead *in sight* (ie that you can actually see on the screen at the time of casting, not that would be theoretically be able to be seen by all your characters) to run away & not attack for the duration of the spell. Firstly, some opponents seem to be unaffected which I've always assumed to be due to a successful spell resistance roll. It seems to work pretty well on low-level undead but as they become more powerful, the chance of resisting seems to improve. Certainly I wouldn't have thought to bother in a room full of Power Liches!Second, the effect will be broken for a particular opponent if you attack it. This will include mass or area affect spells like Mass Fear or Dragon Breath (or another Turn Undead, which counts as an "attack" & cancels the spell on all opponents you can see, and re-applies the spell - with a new spell resistance roll)
