Clockwork Leech

Anesthetizing Bite. When the clockwork leech successfully bites a creature, the creature must succeed on a DC 13 Wisdom (Perception) check to notice the bite. If the leech remains attached to the target, the target can repeat this check at the start of each of its turns.

Immutable Form. The clockwork leech is immune to any spell or effect that would alter its form.

Magic Resistance. The clockwork leech has advantage on saving throws against spells and other magical effects.

Bite. Melee Weapon Attack: +4 to hit, reach 5 ft., one creature. Hit: 5 (1d6 + 2) piercing damage, and the clockwork leech attaches to the target. While attached, the leech doesn't attack. Instead, at the start of each of the clockwork leech's turns, the target loses 5 (1d6 + 2) hp due to blood loss, and the target must succeed on a DC 13 Constitution saving throw or be poisoned until the start of the leech's next turn. The clockwork leech can detach itself by spending 5 feet of its movement. It does so after it drains 10 hp of blood from its target or the target dies. A creature, including the target, can use its action to detach the leech by succeeding on a DC 10 Strength check.

Tail. Melee Weapon Attack: +4 to hit, reach 10 ft., one target. Hit: 7 (1d10 + 2) bludgeoning damage.