Artorias, Custodian of The Morrigan

Aura of Magic Resistance. Artorias and his allies within 30 feet of him have advantage on saving throws against spells and other magical effect.

Aura of the Custodian. Artorias and his allies within 30 feet of him gain a +5 to all saving throws and are immune to the charmed and frightened conditions.

Legendary Resistance (3/day). If Artorias fails a saving throw, he can choose to succeed instead.

Greatsword of Artorias. Artorias' weapon attacks are magical. If he hits a creature of Evil Alignment, the creature takes an additional 11 (2d10) radiant damage (included in the attack).

Raven's Plate. While wearing this adamantine armor, any Critical Hit against Artorias becomes a normal hit.

Eyes of the Custodian. Artorias gains a +5 bonus to initiative, can't be surprised, and other creatures don’t gain advantage on attack rolls against him as a result of being unseen by him.

Spellcasting. Artorias is a 20th-level spellcaster. Its spellcasting ability is Charisma (spell save DC 21, +13 to hit with spell attacks). Artorias has following Paladin spells prepared:
1st level (4 slots): bless, cure wounds, protection from evil and good, sanctuary, searing smite, shield of faith
2nd level (3 slots): branding smite, krail's rupture, lesser restoration, warding bond, wind sprint, zone of truth
3rd level (3 slots): beacon of hope, blinding smite, dispel magic, revivify, spirit shroud
4th level (3 slots): aura of impurity, freedom of movement, guardian of faith, staggering smite, supernal smite
5th level (2 slots): commune, destructive wave, flame strike, greater restoration, summon celestial

Multiattack. Artorias makes three attacks with his greatsword.

Greatsword of Artorias. Melee Weapon Attack: +17 to hit, reach 10 ft., one target. Hit: 18 (2d8 + 9) slashing damage plus 9 (2d8) radiant damage, or 20 (2d10 + 9) slashing damage plus 9 (2d8) radiant damage if wielded with two hands. On a hit with this weapon, if the target is a creature of Evil Alignment they take an additional 11 (2d10) radiant damage.

Lay on Hands (5/day). Artorias can lay hands on himself or another creature within 5 feet of himself, causing the target to regain 25 hit points and cures them of a disease, neutralizes a poison, or ends a spell affecting the creature.

Sentinel Strike. When Artorias hits a creature with an opportunity attack, the creature's speed becomes 0 for the rest of the turn. Creatures provoke opportunity attacks from him even if they take the Disengage action. When a creature within 5 ft. of Artorias makes an attack against a target other than him, he can use his reaction to make a melee weapon attack against the attacking creature.

Artorias 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. Artorias regains spent legendary actions at the start of its turn.

Action (Costs 1 Action). Artorias can make one weapon attack or uses his Lay on Hands.

Spear of the Queen (Costs 2 Actions). Artorias drops into a crouch and readies his sword. He then pounces forward in a piercing dash. Artorias moves in a 50-foot straight line, without provoking opportunity attacks. Every creature within 5 of Artorias' path must succeed on a DC 20 Dexterity saving throw, taking 33 (6d10) piercing damage plus 27 (6d8) radiant damage and is knocked prone. On a successful save, the creature takes only half of the damage and isn't knocked prone.

Raven's Fall (Costs 3 Actions). Spectral raven wings lift Artorias in to the air and Artorias chooses a point within 50 feet. Artorias slams into the ground with immense force on the chosen point. All creatures in a 30-foot radius of Artorias' impact must succeed on a DC 25 Dexterity saving throw, taking 45 (10d8) force plus 45 (10d8) necrotic damage and suffer from one level of exhaustion. On a successful save, the creature only takes half of the damage and does not suffer from one level of exhaustion.