I ran into one in the second spellhold asylum map (before the cat o' 9 lives room). Why can't I get Breach to work on him? Is it immune to 5th level spells or something? I've fired 4 Ruby Rays at it and Breach still does nothing.
Also, remember to bring Potions of Absorbtion with you to Spellhold. They really help against the Amber golems.