Captain Rexius, Herald of Bahamut

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

Aura of Radiant Justice. Captain Rexius exudes an aura radiating divine power in a 30-ft radius. Allied creatures within this aura deal an additional 10 (3d6) radiant damage on weapon attacks. Enemies inside the aura have disadvantage on saving throws against Captain Rexius's spells and abilities.

Vow of Purity. Rexius has sworn an eternal vow to Bahamut in exchange for unmatched purity of heart. He has advantage on all saving throws against spells cast by fiends or undead, and cannot be tainted by necromancy or curses.

Innate Spellcasting. Captain Rexius's innate spellcasting ability is Charisma (spell save DC 21). He can cast the following spells without material components:

At Will: Divine Favor, Shield of Faith, Detect Evil and Good

3/day each: Holy Weapon, Searing Smite (4th level), Dispel Evil and Good

1/day each: Circle of Power, Banishing Smite (6th level), Power Word Heal

Draconic Bond (Crystal Dragon). By his marriage to Tarnisara, a Crystal Dragon, Rexius has gained a magical bond. He can share telepathy with her up to 1 mile. Once per long rest, Tarnisara can summon Rexius to her side or Rexius can summon her (as a Young Crystal Dragon) to his.

Shield of Bahamut. Captain Rexius wields a legendary tower shield blessed by Bahamut himself. When Rexius blocks an attack with the shield, he can choose to reflect radiant damage equal to 10 (1d10+5) back to the attacker (including damage dealt by spells).

Multiattack. Captain Rexius makes three attacks: two with his Radiant Warhammer and one with his Shield Bash.

Radiant Warhammer. Melee Weapon Attack: +15 to hit, reach 10 ft., one target. Hit: 28 (3d12+8) bludgeoning damage plus 18 (4d8) radiant damage. If the target is a fiend or undead, it must succeed on a DC 21 Constitution saving throw or be stunned until the beginning of Rexius's next turn.

Shield Bash. Melee Weapon Attack: +13 to hit, reach 5 ft., one target. Hit: 20 (2d10 + 8) bludgeoning damage. If the target is a Large or smaller creature, it must succeed on a DC 21 Strength saving throw or be knocked prone.

Breath of Bahamut (Recharge 5-6). Captain Rexius exhales a radiant flame in a 60-ft cone. Each creature in the area must make a DC 21 Dexterity saving throw, taking 70 (20d6) radiant damage on a failed save, or half as much on a successful one. Fiends and undead take an additional 10 (3d6) radiant damage.

Captain Rexius 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. Rexius regains spent legendary actions at the start of his turn.

Detect. Captain Rexius makes a Wisdom (Insight or Perception) check.

Radiant Smite. Captain Rexius channels the fury of Bahamut into a weapon attack, adding 10 (3d6) radiant damage to the strike and imposing disadvantage on the target’s next attack if it is a fiend or undead.

Righteous Reposte (Costs 2 Actions). As a reaction to being attacked, Rexius can make one Shield Bash attack. If the attack hits, the attacking creature cannot take reactions until the start of Rexius's next turn.