Longbow of Sticking.

DEX+2 vs AC; 1d10+2 dmg.

From this gnollish bow, your arrow flies true, sticking deep. Until the arrow is removed, each time a melee attack hits your foe, the shock of it drives the arrow deeper and deeper; roll an extra d6 damage on top of each attack.

A humanoid creature can remove the arrow as a standard action on their turn, taking 3d6 damage as they do so and provoking opportunity attacks.