Delusion

Delusion: Whoever wears this device believes it is some other form of useful magical device, and behaves thus (so for example, if Darion believes he is wearing a Ring of Invisibility he will believe himself to actually be invisible). Unlike the potion of the same name, the device's effect is not dispelled by the wearer suffering damage; in fact, the only way to rid a character of this cursed item is with the spell remove curse.