Cassian Basilius

Limited Magic Immunity. Cassian can't be affected or detected by spells of 6th level or lower unless he wishes to be. He has advantage on saving throws against all other spells and magical effects. 

This effect weakens when relics are used against him. 

Fear Aura. Any creature hostile to Cassian that starts its turn within 20 feet of him must make a DC 21 Wisdom saving throw, unless Cassian is incapacitated. On a failed save, the creature is frightened until the start of its next turn. If a creature's saving throw is successful, the creature is immune to Cassian's Fear Aura for the next 24 hours.

Innate Spellcasting. Cassian's innate spellcasting ability is Intelligence (spell save DC _, +10 to hit with spell attacks). Cassian can innately cast the following spells, requiring no material components:

At will: detect thoughts, disguise self, mage hand, minor illusion

3/day each: charm person, detect magic, invisibility, major image, suggestion

1/day each: dominate person, fly, plane shift, true seeing

Service after Death. Whenever a creature dies or goes unconscious , Cassian may touch the creature and transform them into a friendly Revenant. 

The player character may resist their undead servitude/nature upon situations that jog out their humanity. They may then attempt a Wisdom saving throw of 15. 
If the player was killed then transformed, they must roll a Wisdom saving throw of 18.

If the player character makes a successful saving throw, they may use their action to aid their allies, but not act against Cassian Basilius. 

If the player makes 3 consecutive successful saving throws, they break free of Cassian's control, but remain a Revenant until killed. 

Cast a Spell. Cassian can cast any spell up to 9th level from any Wizard school spell list that he has prepared.

Kingly Blade. Cassian can use a Radiant Great Sword that does 6 d6 + 5 damage and a construction saving throw of 16 will need to be made, or the target is blinded till they make a successful saving throw at the end of their turn. 

Dimension Door (Costs 2 Actions). Cassian is able to cast on will in any direction up to 500 feet that he knows of or can see, and teleports to that area.

Cassian can take anyone or any object with him that is his size or smaller if successfully grappled. 

If Cassian would arrive in a place already occupied by an object or a creature, Cassian and any creature traveling with him each take 4d6 force damage, and the spell fails to teleport him.

Disrupt Life (Costs 3 Actions). Cassian can manipulate the souls of the living characters but not on undead beings.

Each non-undead target within 20 feet of the creature must make a DC 18 Constitution saving throw against this magic, taking 21 (6d6) necrotic damage on a failed save, or half as much damage on a successful one.

Cantrip (Costs 1 Action). Cassian can cast 1 Cantrip of his choice.

Cassian casts a cantrip from his Cantrip List.