Aspect of Atropus

Legendary Resistance (3/Day). If the Aspect of Atropus fails a saving throw, it can choose to succeed instead.

Regeneration. The Aspect of Atropus regains 15 hit points at the start of its turn. If the Aspect of Atropus takes radiant damage, this trait doesn't function at the start of the Aspect of Atropus next turn. The Aspect of Atropus dies only if it starts its turn with 0 hit points and doesn't regenerate.

Magic Resistance. The Aspect of Atropus has advantage on saving throws against spells and other magical effects.

Negative Energy Aura. Creatures within 30 feet of the aspect of atropus can’t regain hit points, and any creature that starts its turn within 30 feet of the aspect of atropus takes 17 (3d10) necrotic damage.

Turn Resistance Aura. The aspect of atropus and any other undead creature within 30 feet of it has advantage on saving throws against any effect that turns undead.

Undeath Aura. Any Creature within 30 feet of the aspect of atropus that dies, returns as an undead creature under the aspect of atropus' control. Creatures return in 1d4 rounds and take either the form of a zombie or a skeleton as if raised by animate dead

Immutable Form. The Aspect of Atropus is immune to any spell or effect that would alter its form.

Spellcasting. The Aspect of Atropus counts as an 20th level caster Charisma is it's spellcasting ability. (Spell save DC 23, +15 to hit with spell attacks)

Cantrips (At Will) Chill Touch, Toll the Dead

1st Level (At Will) Cause Fear, Inflict Wounds

2nd Level (At WIll) Blindness/Deafness, Ray of Enfeeblement 

5th Level (4 Slots) Enervation, Negative Energy Flood, Blight, Vampiric Touch

6th Level (1 Slot) Circle of Death

7th Level (1 Slot) Finger of Death

8th Level (1 Slot) Maddening Darkness

9th Level (1 Slot) Meteor Swarm

Multiattack. The Aspect of Atropus can make 3 slam attacks, or it can substitute 1 slam attack for its life drain ability. It can substitute it's multiattack option to cast a spell, or use one if it's other abilities. 

Slam. Melee Weapon Attack: +17 to hit, reach 5 ft., one target. Hit: 17(3d10) necrotic damage.

Life Drain. The aspect of atropus targets one creature it can see within 120 feet of it. The target must succeed on a DC 23 Constitution saving throw, taking 36 (8d8) necrotic damage on a failed save, or half as much damage on a successful one. The aspect of atropus regains a number of hit points equal to half the amount of damage dealt.

Divine Scourge (Recharge on 6). The aspect of atropus released it's vile nature onto land. Any Divine spellcaster (Cleric, Druid, Paladin) or extraplanar outsider (Such as, but not limited to Angels, Demons, Devils.) must succed a DC 23 constitution saving throw or become poisoned (this ability ignores immunity to the poisoned condition) for 1d4 days. on a failed save taking 56 (10d10) Vile damage. 

Constitution Drain (Recharge on 6). The Aspect of Atropus makes a slam attack on a hit target must succeed a dc 23 Constitution saving throw, taking 1d4 constitution drain. A creature who's constitution score becomes 0 dies. 

The aspect of atropus can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature’s turn. The aspect of atropus regains spent legendary actions at the start of its turn.

Slam. The aspect of atropus makes a slam attack.

Wail (Costs 3 Actions). The aspect of atropus lets out a withering wail. Any creature within 120 feet of the aspect of atropus that can hear the wail must succeed on a DC 23 Constitution saving throw or gain 1 level of exhaustion.