Not sure if this is a bug or not--it might be an unintended behavior after changing the behavior of certain monsters to stay on the temple level.

I was playing a ratling wizard who cast burning hands in the AF and angered all the trees. Well, I thought I would show them who's boss by luring the banshee up to the forest, which is always good for a laugh if you can manage it.

She followed me up a couple of flights of stairs, but wouldn't follow me to the water temple level.