once i'm in the sphere how do i defeat the clay golem ,everytime i hit it it says golem was immune to my damage or something like that can anyone help me?

Clay golems can only be beaten with blunt weapons.

You should be able to kill it with +3 (or higher) weapons, i killed all the golems in nalia's keep with the blade of roses...also enchant weapon spell comes in handy for golems

No, Armisael is right, only +1 blunt weapons work on clay golems, but for the others you need any +2, except iron which need +3. For a grin reduce the iron golems magic resistance and cast domination, then watch them squish the other golems.