Dagger of Venom (Dagger of Venom +2 in-game) is an enchanted dagger which poisons the victim.
In BG1, it's one of the most powerful daggers, an excellent mage interrupter, for sale at the Thunderhammer Smithy with a steep price tag.
|“||This dagger is a potent blade favored by assassins all across the realms. This particular dagger of venom was created for use by the Shadow Thieves of Amn. Every time it hits an opponent, it secretes a venom into the bloodstream of the creature. The venom works quickly and efficiently.||”|