Ankle Biter

Goblin Only. If you are the target of a grapple or similar combat maneuver, you can, as a reaction, attempt to bite your opponent in addition to any attacks of opportunity or other consequences your opponent might incur from attacking you. This natural attack deals base damage appropriate for a creature of your current size (usually 1d4+str for Small creatures). If grappled or pinned, you can continue to make this additional bite attack each round as a bonus action on your turn. You gain a bonus on any attempt to break the grapple equal to the damage you dealt with your bite that round.