Ive heard of a helmet which reverses alignment does anyone know where it is i think it is in durlags tower if so which floor?

It's VERY hidden, so you won't find it without a spoil.

So, SPOILER.
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The Demonknight has it on him, but only when he appears on the ground floor. After he teleports away, you can only get the helm with gatekeeper.

To kill the demonknight, you need to cast otiluke's resilient sphere (sp) on him. Your characters then punch him (yes, you did read right), until he falls unconcious. Dispel magic on him and then magic missile to finally kill him (can't remember if arrows etc. work, but MM did for me). You get some other goodies, but the helm is the main prize.

Don't forget to take potions of strength and be prepared to cast the sphere again if you don't knock him out in time.