Blood Wraith

Liquid Form. The blood wraith can enter a hostile creature's space and stop there. It can move through a space as narrow as 1 inch wide without squeezing.

Freeze. If the blood wraith takes cold damage, it partially freezes; its speed is reduced by 20 feet until the end of its next turn.

Sunlight Sensitivity. While in sunlight, the blood wraith has disadvantage on attack rolls, as well as on Wisdom (Perception) checks that rely on sight.

Blood Siphon. Melee Weapon Attack: +6 to hit, reach 5 ft., one creature. Hit: 21 (4d8 + 3) necrotic damage. The target must succeed on a DC 14 Constitution saving throw or its hit point maximum is reduced by an amount equal to the damage taken. This reduction lasts until the target finishes a long rest. The target dies if this effect reduces its hit point maximum to 0.

Whelm (Recharge 5–6). Each creature in the wraith's space must make a DC 15 Strength saving throw. On a failure, a target takes 13 (2d8 + 4) necrotic damage. If it is Large or smaller, it is also grappled (escape DC 14). Until this grapple ends, the target is restrained and unable to breathe. If the saving throw is successful, the target is pushed out of the wraith's space.

Create Specter. The wraith targets a humanoid within 10 feet of it that has been dead for no longer than 1 minute and died violently. The target's spirit rises as a specter in the space of its corpse or in the nearest unoccupied space. The specter is under the wraith's control. The wraith can have no more than seven specters under its control at one time.