Giant Leech 2014

Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 5 (1d4 + 3) piercing damage, and the leech attaches to the target. While attached, the leech doesn't attack. Instead, at the start of each of the leech's turns, the target loses 5 (1d4 + 3) hp due to blood loss.

The leech can detach itself by spending 5 feet of its movement. It does so after it drains 15 hp of blood from the target or the target dies. A creature, including the target, can use its action to detach the leech.