Bahamut

Arcane Mastery. Bahamut knows every cantrip and can cast them without material components.

Discorporation. When Bahamut drops to 0 hit points or dies, his body is destroyed but his essence travels back to his domain in Celestia, and he is unable to take physical form for a time.

Disintegrating Roar (3/Day). Bahamut emits a powerful roar. Any Large or smaller nonmagical object or creation of magical force within 100 feet of Bahamut is disintegrated. If the object or creation of force is Huge or larger, a 10 foot cube portion of it is disintegrated. Each creature within 100 feet of Bahamut and able to hear the roar must make a DC 27 Constitution saving throw. On a failed save, a creature suffers the effects of the disintegrate spell and is permanently deafened.

Divine Intuition. Bahamut can try to cast a spell the he doesn't know. When he does, he makes an Intelligence (Arcana) check. If the check succeeds, he casts the spell. If the check fails, so does the spell, and the action used to cast the spell is wasted. The DC starts at 22 for 1st-level spells and increases by 2 for each level above 1st.

Innate Spellcasting. Bahamut's innate spellcasting ability is Charisma (spell save DC 27). Bahamut can innately cast the following spells, requiring no material components:

At will: calm emotions, comprehend languages, heroism

3/day each: greater restoration, polymorph

1/day each: holy aura, true polymorph

Legendary Resistance (5/Day). If Bahamut fails a saving throw, it can choose to succeed instead.

Limited Magic Immunity. Unless he wishes to be affected, Bahamut is immune to spells of 6th level or lower. He has advantage on saving throws against all other spells and magical effects.

Magic Weapons. Bahamut's Weapon attacks are magical.

Regeneration. Bahamut regains 32 hit points at the start if his turn.

Voice of Reason. Bahamut can communicate telepathically with any creature within 500 feet of him. The creature must have an Intelligence of 4 or higher but it does not need to know any languages. Bahamut has advantage on Wisdom (persuasion) checks to convince an enemy to surrender.

Multiattack. Bahamut can use his frightful presence. He then makes three attacks: two with his claw and one with his tail.

Claw. Melee Weapon Attack: +19 to hit, reach 15 ft., one target. Hit: 24 (4d6 + 10) slashing damage.

Tail. Melee Weapon Attack: +19 to hit, reach 25 ft., one target. Hit: 28 (4d8 + 10) piercing damage.

Frightful Presence. Each creature of Bahamut's choice that is within 240 feet of Bahamut and aware of him must succeed on a DC 27 Wisdom saving throw or become frightened for 1 minute. A creature can repeat the saving throw at the end of each of its turns, ending the effect on a success. If a creature's saving throw is successful or the effect ends for it, the creature is immune to Bahamut's Frightful Presence for the next 24 hours.

Change Shape. The dragon magically transforms into any humanoid or beast, while retaining its game statistics (other than his size). This transformation ends if the dragon is reduced to 0 hit points or if it uses a bonus action to end it.

Bahamut can take 5 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. Bahamut regains all spent legendary actions at the start of its turn.

Bite. Melee Weapon Attack: +19 to hit, reach 20 ft., one target. Hit: 32 (4d10 + 10) slashing damage plus 14 (4d6) radiant damage.

Cold Breath (Costs 2 Actions). Bahamut breathes an icy blast in a 90-foot cone. Each creature in that area must make a DC 27 Dexterity saving throw, taking 72 (16d8) cold damage on a failed save, or half as much damage on a successful one.

Exalting Breath (Costs 2 Actions). Bahamut exhales the restoring winds of Mount Celestia in a 90-foot cone. Each creature in that area of Bahamut's choice regains 88 (16d10) hit points, and each creature in that area of Bahamut's choice that has been dead for no longer than 1 hour is restored to life with all its hit points.

Platinum Breath (Costs 2 Actions). Bahamut exhales radiant platinum flames in a 90-foot cone. Each creature in that area must make a DC 27 Dexterity saving throw, taking 77 (14d10) radiant damage on a failed save, or have as much on a successful one.

Vaporizing Breath (Costs 3 Actions). Bahamut exhales a magical vapor in a 90-foot cone. Each creature in that area must make a DC 27 Constitution saving throw. On a failed save, a creature suffers the effects of the gaseous form spell. At the end of each of its turns, an affected creature can make another Constitution saving throw. On a success, the spell ends for that creature