Dagger of the Snake

Source: Natalie's Setting

Dagger, uncommon

You can use an action to cause thick, black poison to coat the blade. The poison remains for 1 minute or until an Attack using this weapon hits a creature. That creature must succeed on a DC 15 Constitution saving throw or take 2d10 poison damage and become Poisoned for 1 minute. The Dagger can't be used this way again until the next dawn.