Unseelie Guardian

Legendary Resistance (2/Day). If the Unseelie Guardian fails a saving throw, they can choose to succeed instead.

Fey Ancestry. The Unseelie Guardian has Advantage on saving throws to avoid or end the Charmed or Frightened condition.

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

Divine Smite. Unseelie Guardians always have the divine smite spell prepared. In addition, they can cast it without expending a spell slot, once per Long Rest.  Unseelie Guardians Divine Smite uses necrotic damage instead of radiant.

Spellcasting. The Unseelie Guardian is a 15th-level spellcaster. Its spellcasting ability is CHA (spell save DC 18, +10 to hit with spell attacks). The Unseelie Guardian has following Paladin and Cleric spells prepared:

1st level (4 slots): command, compelled duel, searing smite

2nd level (3 slots): hold person, magic weapon

3rd level (3 slots): dispel magic, elemental weapon, cure wounds

4th level (3 slots): staggering smite, blinding smite, mass healing word

5th level (3 slots): circle of power, destructive wave, mass cure wounds

6th level (2 slots): heal, blade barrier, word of recall

7th level (1 slot): regenerate

8th level (1 slot): antimagic field

Multiattack. The Unseelie Guardian makes three attacks per action.

Onyx Scimitar. Melee Weapon Attack: +12 to hit, reach 5 ft., one target. Hit: 15 (2d6 + 9) slashing damage.

Divine Smite. Cast divine smite and expend a spell slot.

Parry. The Unseelie Guardian adds 6 to its AC against one melee attack that would hit it. To do so, the Unseelie Guardian must see the attacker and be wielding a melee weapon.