Lamprey of Tuonela

Amphibious. The lamprey can breathe air and water.

Multiattack. If it isn’t attached to a creature, the lamprey makes one Bite attack and one Water Pull attack.

Bite. Melee Weapon Attack: +6 to hit, reach 5 ft., one creature. Hit: 8 (1d8 + 4) piercing damage, and the lamprey attaches to the target. While attached, the lamprey can’t make Bite attacks. Instead, the target takes 8 (1d8 + 4) necrotic damage at the start of each of the lamprey’s turns. The lamprey can detach itself as a bonus action. A creature, including the target, can use its action to do a DC 13 Strength check to detach the lamprey.

Water Pull. The Lamprey creates a wave towards it. Every creature within 15 ft. of the lamprey has to make DC 13 Strength saving throw or be pulled next to the lamprey.