> This example was taken from Unrest but it has also
> happened to me once in Beholder and I have read
> that it occurs in almost every other dungeon also.

Another notable place this happens is the Mino caves in Steamfront. It's not
z-axis but side to side in large distances. Maldrath or whatever his name
is, seems to be able to cast a spell on you from his little spot no matter
where you are in the caves.