SRD:Dagger of Venom
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Dagger of Venom: This black +1 dagger has a serrated edge. It allows the wielder to use a poison effect (as the spell, save DC 14) upon a creature struck by the blade once per day. The wielder can decide to use the power after he has struck. Doing so is a free action, but the poison effect must be invoked in the same round that the dagger strikes.