Actions

Multiattack. The vampire makes two attacks, only one of which can be a bite attack.   Unarmed Strike. Melee Weapon Attack: +9 to hit, reach 5 ft., one target. Hit: 8 1d8+4 bludgeoning damage. Instead of dealing damage, the vampire can grapple the target (escape DC 18).   Bite. Melee Weapon Attack: +9 to hit, reach 5 ft., one willing creature, or a creature that is unable to move. Hit: 9 2d8 necrotic damage. The target's maximum hp is reduced by the amount of damage dealt, and the vampire regains that much hp. The reduction lasts until the target finishes a long rest. The target dies if this effect reduces its hit point maximum to 0.   Charm. The vampire targets one humanoid it can see within 30 feet of it. If the target can see the vampire, the target must succeed on a DC 14 Wisdom save or be charmed by the vampire. The charmed target regards the vampire as a trusted friend to be heeded and protected. Although the target isn't under the vampire's control, it takes the vampire's requests or actions in the most favorable way it can, and it is a willing target for the vampire's bite attack.
Each time the vampire or the vampire's companions do anything harmful to the target, it can repeat the saving throw, ending the effect on itself on a success. Otherwise, the effect lasts 24 hours or until the vampire is destroyed, is on a different plane of existence than the target, or takes a bonus action to end the effect.   Children of the Night (1/Day). The vampire magically calls 2d4 swarms of bats or rats, provided that the sun isn't up. While outdoors, the vampire can call 3d6 wolves instead. The called creatures arrive in 1d4 rounds, acting as allies of the vampire and obeying its spoken commands. The beasts remain for 1 hour, until the vampire dies, or until the vampire dismisses them as a bonus action.