Stinger

This shortsword once belonged to a legendary assassin whose victims were often reported to die
from the venom of a wyvern stinger. This shortsword grants a +1 to attack and damage. In addition, on a critical hit, a creature takes 3d8
poison damage and must succeed on a DC 13 Constitution saving throw or be poisoned for 1
minute. While poisoned in this way, a creature
takes 1d8 poison damage at the start of each of its
turns and can repeat the saving throw at the
end of its turns.