Barrowghast

Any creature that starts its turn within 10 feet of the barrowghast must make a DC 16 Constitution saving throw. On a failed save, the creature has the Poisoned condition for 1 minute. While Poisoned this way, the creature can't regain hit points. On a successful save, the creature is immune to the Stench of all barrowghasts for 24 hours.

The barrowghast makes two Slam attacks. It can replace one Slam attack with a Life Drain attack.

Melee Weapon Attack +8 to hit, reach 10 ft., one target. 18 (2d12 + 5) Bludgeoning damage.

Melee Weapon Attack +8 to hit, reach 10 ft., one creature. 9 (1d8 + 5) Necrotic damage, and the target must succeed on a DC 16 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.
A Humanoid slain by this attack immediately rises as a zombie (see the Monster Manual). The zombie acts as an ally of the barrowghast but isn't under its control.

Immediately after the barrowghast takes piercing or Slashing damage, poisonous ichor sprays from the wound. Each creature within 5 feet of the barrowghast must make a DC 16 Dexterity saving throw, taking 10 (3d6) Poison damage on a failed save, or half as much damage on a successful one.