Entity: Venomtail Kobold

Source Player Core 2 pg. 21 ^1.1

Thanks to the proximity of a venomous creature to your warren, you were born with a vestigial spur in your tail that secretes deadly venom. You gain the Tail Toxin action.

Tail Toxin (manipulate) Frequency once per day; Requirements You are wielding a piercing or slashing weapon; Effect You apply your tail's venom to a piercing or slashing weapon. If your next Strike with that weapon before the end of your next turn hits and deals damage, you deal persistent poison damage equal to your level to the target.