Currently, a cursed potion of invisibility is one of the most overpowered items in all of ADOM. If the potion is cursed, it can be thrown at *any* enemy to cause a blinding effect, rendering them unable to cast spells, walk normally, or fight effectively. Most monsters under this effect will only hit you about 1/3 as often as they would without being blind. The most egregious problem with this item is that it works on *all* bosses, including Andor Drakon himself! Using the potion on Andor makes the fight ridiculously easy, and is kind of anti-climactic for what's supposed to be a fight over the fate of the world.

My suggestion is this: Make cursed potions of invisiblity work *only* on non-boss monsters. Monsters like Andor, Keriax, the Ancient Chaos Wyrm, etc. should all be immune to the effect.

EDIT: As Grond mentioned below, this should probably apply to all items that can cause blindness.