First of all, welcome to the board
Uhm, you killed the Lich (for the golden arms en legs)and you find the Beholder difficult??????? Beholders have a weakness for good fighters
. Try minsc his rage, protects you from some charm spells. Lots of physical damage you need to kill those, but you have to do it quick. Also an item that reflects spells (or the spell : spellturning). The big cheese (the eye itself) is easily beaten when you use the rod on it, if it doesnt get down still, get minsc to work it
Hope this helps.
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There's something in your eyes, ah no, I see now, it's the reflection of my deadly gaze - Mirac Honorguard
(Necromancer)