Archknight of Arvaal

Draconic Advantage. While wearing the blue dragon scale mail, the archknight has advantage on saving throws against the Frightful Presence and breath weapons of dragons.

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

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

Marshal Undead. Unless the archknight is incapacitated, he and undead creatures of his choice within 60 feet of hiim have advantage on saving throws against features that turn undead.

Special Equipment. The archknight is attuned to a ascendant white dragon's wrath longsword, a shield of the uven rune, and a blue dragon scale mail. He also wields a ring of water walking and uses a saddle of the cavalier when riding a mount (all accounted for in his statistics).

Unusual Nature. The archknight doesn’t require air, food, drink, or sleep.

Multiattack. The archknight makes two melee weapon attacks or three ranged weapon attacks.

Ascendant White Dragon's Wrath Longsword. Melee Weapon Attack: +14 to hit, reach 5 ft., one target. Hit: 12 (1d8 + 8) slashing damage, or 13 (1d10 + 8) slashing damage if used with two hands, plus 10 (3d6) cold damage and 18 (4d8) necrotic damage.

Additionally, whenever the archknight rolls a 20 on his attack roll with this weapon, each creature of his choice within 5 feet of the target takes 5 cold damage.

Javelin. Melee or Ranged Weapon Attack: +11 to hit, reach 5 ft. or range 30/120 ft., one target. Hit: 8 (1d6 + 5) piercing damage plus 18 (4d8) necrotic damage.

Bane (Recharges after a Short or Long Rest). While attuned to the shield of the uven rune, the archknight can cast the bane spell from the shield (save DC 17). The spell does not require concentration and lasts for 1 minute.

Cold Cone (1/Day). While attuned to the ascendant white dragon's wrath longsword, the archknight can unleash a 60-foot cone of destructive cold from the sword. Each creature in that area must make a DC 18 Dexterity saving throw, taking 42 (12d6) cold damage on a failed save, or half as much damage on a successful one.

Detect Dragon (1/Day). While wearing the blue dragon scale mail, the archknight can focus his senses to magically discern the distance and direction to the closest blue dragon within 30 miles of him.

Hellfire Orb (1/Day). The archknight hurls a magical ball of fire that explodes at a point he can see within 120 feet of him. Each creature in a 20-foot-radius sphere centered on that point must make a DC 19 Dexterity saving throw. The sphere spreads around corners. A creature takes 35 (10d6) fire damage and 35 (10d6) necrotic damage on a failed save, or half as much damage on a successful one.

Spellcasting. The archknight casts one of the following spells, requiring no material components and using Charisma as the spellcasting ability (spell save DC 19):

3/day each: command, compelled duel, dispel magic, hold person

 2/day each: banishment, destructive wave (necrotic)

Deadly Rebuke. While attuned to the shield of the uven rune, immediately after a creature hits the archknight with a melee attack, he can deal 10 (3d6) necrotic damage to that creature.

Parry. The archknight adds 7 to his AC against one melee attack that would hit him. To do so, the archknight must see the attacker and be wielding a melee weapon.

The archknight 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 archknight regains spent legendary actions at the start of his turn.

Attack. The archknight makes one weapon attack.

Charge (Costs 2 Actions). The archknight moves up to his speed or commands a mount he is riding to move up to its speed. This movement doesn’t provoke opportunity attacks. 

Cast a Spell (Costs 3 Actions). The archknight uses Spellcasting.

Quick Escape (Costs 3 Actions). The archknight mounts or dismounts a creature he is riding.