Joker Cards (5e Equipment)
From D&D Wiki
Weapon (playing card), very rare (requires attunement)
This is a deck of 52 playing cards. Each card uses the statistics of a dart.
You have a +1 bonus to attack and damage rolls made with these magic weapons.
When you hit a creature with a joker card, the target must succeed a DC 14 Constitution saving throw or take 2d10 poison damage and be poisoned for 1 minute. A poisoned creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.
Once an attack has been made with a card, it becomes a normal playing card.