Bahamut - King of the Dragons

Heart of the Dragons. Upon being struck by a critical hit, Bahamut regains use of his Draconic Breath attack.

Soul of the Dragons. Bahamut regains 75 hit points whenever a Spectral Dragon created by Will of the Dragons is destroyed.

Legendary Resistance (6/Day). If Bahamut fails a saving throw, it can choose to succeed instead.

Red Haze of War. Bahamut constantly emits an aura of warfare. Each creature within 200ft of Bahamut at the start of their turn must make a DC 17 Wisdom saving throw. On a failed save, that creature is blinded by bloodlust and is forced to take the attack action against the closest creature to them. The affected creature can still use bonus actions and movement, as long as all movement was not used up attempting to get to the closest creature. If the closest creature cannot be reached, then the affected creature uses its action to dash towards the creature instead.

Multiattack. Bahamut makes three attacks: two Dragon Greatsword attacks, and a bite attack. If a Spectral Dragon or any Chromatic Dragon is not currently within 60ft of Bahamut, he may then also use Will of the Dragons.

Dragon Greatsword. Melee Weapon Attack: +17 to hit, reach 15 ft., one target. Hit: 41 (6d10 + 8) slashing damage. 

Bite. Melee Weapon Attack: +17 to hit, reach 10 ft., one target. Hit: 21 (2d12 + 8) piercing damage. If this attack hits, the target must make a STR save, DC 20. On a failed save, the target is restrained and can only use their action to try and escape Bahamut's mouth by repeating the saving throw. While restrained by this action, if Bahamut uses his Draconic Breath attack, the creature automatically fails the saving throw, takes double the damage, and is no longer restrained.

Draconic Breath (Recharge 6). Bahamut exhales its' choice of either fire, ice, or lightning in a 90-foot cone. Each creature in that area must make a DC 21 Dexterity saving throw, taking 81 (18d8) fire, ice or lightning damage on a failed save, or half as much damage on a successful one.

Will of the Dragons. Bahamut summons a Spectral Adult Red Dragon, Adult Blue Dragon or Adult White Dragon to fight with him. This dragon has its maximum HP halved.

Bahamut 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 tarrasque regains spent legendary actions at the start of its turn.

Wingbeat. Bahamut powerfully beats its wings. Any creature within 15ft of Bahamut must make either a DC 22 Dexterity or Strength save. On a failed save, that creature takes 9 (2d8) bludgeoning damage, is pushed 60ft away, and is knocked prone. On a successful save, the creature is pushed 15ft away instead and takes no damage.

Tail slam. If a creature is behind Bahamut, it slams its tail down onto that creature. That creature must make a DC 18 Dexterity save, or take 60 (8d12 + 8) bludgeoning damage and be knockedprone.

Warcry (Costs 2 Actions). Bahamut lets out an almighty roar, sending his enemies into disarray. Each creature who can hear the roar up to 300ft away from Bahamut must make a DC 19 Wisdom save, 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 itself on a success. If a creature's saving throw is successful or the effect ends for it, the creature is immune to Bahamut's Warcry for the next 24 hours.