Helm of Ghostly Defense
This misty helmet allows you to resist some necrotic damage and can be activated to turn you insubstantial for a short time.
Head Slot 325,000 gp
Gain resist 10 necrotic.
Power Encounter (Immediate Interrupt)
You can use this power when you are hit by an attack. You become insubstantial until the start of your next turn.
Published in Player's Handbook, page(s) 248.