This reminds me of the single best cursed magic item for D&D I ever gave to a player. It was named Milo's Folly. It was a +2 semi-intellegent bane (arachnids) short sword created via a (poorly worded) wish spell. It's primary power was the ability to detect all spiders within 1 mile at all times. It would let the owner know telepathically/empathically where all of those spiders were. Note, that I did not say "monstrous spiders". This constant reminder of where every spider from speck sized up to Shelob sized made the user paranoid that the spiders were in fact out to get him (or her). Yes, Milo the halfling rogue poorly worded his wish.