Corpsemaker

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

Bringer of Death. The corpsemaker deals an extra 3d10 Necrotic damage to any creature it hits with an attack if that creature is marked with a Brand of Death. Additionally, the number the corpsemaker needs to roll to land a critical hit on a creature marked with a Brand of Death is reduced by 1.

Death Burst. When the corpsemaker dies, it explodes, forcing all creatures within 90 feet of it to make a DC 21 Constitution saving throw or take 13d10 Necrotic damage and gain one level of Exhaustion. Creatures that pass the save take half as much damage only. Creatures marked with a Brand of Death have disadvantage on the save.

Multiattack. The corpsemaker uses Mark for Destruction if it can. It then makes three slam attacks.

Slam. Melee Weapon Attack: +14 to hit, reach 15 ft., one target. Hit: 24 (3d6 + 14) Bludgeoning damage.

Mark for Destruction (Recharge 5–6). The corpsemaker magically marks a target with a Brand of Death. While branded in this way, the creature is vulnerable to Necrotic damage, and must succeed a DC 17 Wisdom saving throw whenever it takes Necrotic damage. If the creature fails the save, it becomes Frightened of the source of the necrotic damage until the end of it's next turn.

Annihlate (1/day). The corpsemaker magically detonates one target it can see that is marked with a Brand of Death. The target must succeed a DC 24 Constitution saving throw. If the creature succeeds the save, it takes 13d10 Necrotic damage, and is unable to take actions until the end of it's next turn. If the creature fails the save, it takes 333 necrotic damage, or 113 of it is a Celestial. If the creature dies from this damage, the corpsemaker can chose any number of creatures within 60 feet of the original target. These creatures each take 13 necrotic damage and become marked with a Brand of Death. Whether it succeeds or fails the save, the target of this ability is no longer marked with a Brand of Death.

Innate Spellcasting. The corpsemaker casts Toll the Dead as a level 17 spellcaster.

Will of Orcus (1/day). The corpsemaker casts Create Undead. It can cast this spell even if it isn't night.