Here is what happened when trying to uncurse the Staff of Doom:

1. Valkyrie casts Remove Curse on Bishop. Spell backfires, and the Valkyrie is now hexed. (Did you know that spell could backfire?)

2. Bishop casts Remove Curse on Valkyrie. The hex is only reduced, not cured, even though the spell was not cast at the maximum possible level. (There's no option to choose the power level of that spell.)

Isn't that strange?

By the way, my level 14 Bishop isn't able to uncurse the Staff of Doom without a spell. Remove Curse needs to be cast at power level 5 to uncurse it.

And of course, some more casts later and the game crashes with the following message: I suspect this might be caused by the character having negative SP after casting Remove Curse, having it backfire, and becoming hexed.