Cleanser of Shadows

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

Angelic Weapons. The Cleanser's weapon attacks are magical. When the deva hits with any weapon, the weapon deals an extra 4d8 radiant damage (included in the attack).

Horde Warden. Creatures cannot benefit from flanking against the Cleanser. The Cleanser's Armor Class increases by one for every creature that is within melee range of it. 

Grave Guide. When an Undead creature is reduced to 0 hit points by the Cleanser, it dies immediately.  

Innate Spellcasting. The Cleanser's spellcasting ability is Charisma (spell save DC 16). The Cleanser can innately cast the following spells, requiring only verbal components:

At will: protection from evil and good

1/day each: greater restoration, flame strike

Multiattack. The Cleanser makes three attacks with its Halberd or Smite attacks.

Halberd. Melee Weapon Attack: 10 to hit, reach 15 ft., 1 target. Hit: 17 (2d10 + 6) slashing damage and 18 (4d8) radiant damage.

Smite. Lightning courses down from the heavens into a point the Cleanser can see within 120 ft. Creatures within 10 ft of this point must make a DC 17 Dexterity saving throw or take 22 (4d10) lightning damage. 

Attract Undead (Once per Short Rest). The Cleanser raises their Angelic Halberd and radiates a luring vitality that draws the hunger the undead. All undead within 1 mile become aware of the presence and location of the Cleanser. They must make a DC 16 Wisdom saving throw, or begin moving toward the Cleanser using their action to dash. Once in range, the undead attack the Cleanser. This influence ends if the undead takes damage.  

Destroy Undead (Once per Short Rest). The Cleanser strikes the ground with their Halberd, blasting celestial wrath in a 30 ft radius. Undead creatures within the area must make a DC 17 Wisdom saving throw. On a failed saving throw, creatures with a challenge rating of 3rd or lower are instantly destroyed. Undead with a challenge rating of 4 or higher suffer a wave of power dealing 36 (8d8) radiant damage. On a successful saving throw, the creatures suffer half the 8d8 radiant damage.  

Absorb Animation. When an undead creature the Cleanser can see within 60 ft drops to zero hit points, the Cleanser can use a reaction to draw energy from the corpse. The body of the creature turns to dust and the Cleanser has advantage on attack rolls until the end of its next turn.