Assisi the Faultless

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

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

Bloodied and War-Strong. When Assisi reduces a hostile creature to 0 hit points, he gains 1d10 temporary hit points. Additionally, when he falls below 10 Hp he can add his charisma modifier to all attacks.

Rite of the Hecatomb. When Assisi is reduced to 0 hp he drops to 1 hp instead. He then siphon the blood of nearby foes within 15 feet, dealing 1d12 + 10 damage to each target within range. In doing so, He regains 1d12 hp for each creature damaged. 

Spellcasting. Assisi is a modified 10th-level spellcaster. His spellcasting ability is Charisma (spell save DC 17, +9 to hit with spell attacks). He has the following spells prepared:

Cantrips (at will): Bloodletting of Lord Anicetus, thaumaturgy

1st level (3 slots): Toll The Dead, Cause Fear, shield of faith

2nd level (2 slots): Tasha's Mind Whip, Bloodward, spiritual weapon

3rd level (2 slots): animate dead, dispel magic

4th level (2 slots): Gate Seal, Shadow of Moil

5th level (1 slots): Antilife Shell, Geas

6th level (1 slot): Bones of the Earth

Multiattack. Assisi makes 4 attacks with Cruamnis

Cruamnis. Melee Weapon Attack: 1d10+6. On a hit, the target must make a DC 16 Constitution saving throw or take 1d8 bleeding damage at the start of each of its turns. This damage decreases by 1 each turn, for a maximum of -7. To end this effect, the target may repeat the Constitution save, after each instance of damage, or have another creature successfully perform a DC 17 medicine check to stanch the bleeding. 

No Deserters. Assisi is prepared to attack those who break lines. Assisi may perform an attack of opportunity in addition to another bonus action. 

Parry. Assisi adds 2 to his AC if targeted by an attack that would otherwise hit. He must be wielding a melee weapon and be able to see the attacker. 

Assisi 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 mummy lord regains spent legendary actions at the start of its turn.

Cantrip(Costs 1 Action). Assisi The Faultless casts a cantrip

Advance(Costs 1 Action). Assisi moves up to his speed. Alternatively, up to five allies that can see and hear the Assisi can use their reactions to move up to half their speeds

Cause Fear(Costs 2 Actions). Assisi casts Cause Fear. When cast in this way, it does not consume a spell slot. 

Inspiring Leader(Costs 1 Action). Assisi targets up to five allies it can see within 30 feet of it. Each ally gains temporary hit points equal to 2d8 + Assisi's Charisma modifier.

Blood Tribute (Costs 2 Action). Assisi the Faultless commands all to give life to him. If a creature Assisi can see would regain hit points, Assisi gains them instead.

Soul of the Ice Bear. (Costs 3 Actions). Assisi the Faultless summons an aspect of his spirit animal, the Ice-Bear. Shielded in its aura he gains 5d10+15 temporary hit points. He makes a Multiattack as a polar bear. The bear aura along with the temporary HP it gives can be removed from Assisi with Dispel Magic.