Buttercup

Legendary Resistance (4/Day). If Buttercup fails a saving throw, she can choose to succeed instead.

Metallic Awakening (Recharges after a Short or Long Rest). If Buttercup would be reduced to 0 hit points, her current hit point total instead resets to 450 hit points, she recharges her Breath Weapons, and she regains any expended uses of Legendary Resistance. Additionally, Buttercup can now use the options in the “Mythic Actions” section for 1 hour. 

Unusual Nature. Buttercup doesn’t require food or drink.

Draconic Loyalty. Buttercup and Sir Golder of the Highlands share a special bond forged from hundreds of years of service and kinship. Due to this, both Buttercup and Sir Golder can feel the emotions and current health of the other, granted they are both on the same plane of existence. 

Multiattack. Buttercup can make one Bite attack from each of her heads and two claw attacks.

Bite. Melee Weapon Attack: +18 to hit, reach 15 ft., one target. Hit: 21 (2d10 + 10) piercing damage plus 13 (2d12) force damage.

Claw. Melee Weapon Attack: +18 to hit, reach 10 ft., one target. Hit: 19 (2d8 + 10) slashing damage. If the target is a Huge or smaller creature, it is grappled (escape DC 20) and is restrained until this grapple ends. Buttercup can have only one creature grappled in this way at a time.

Tail. Melee Weapon Attack: +18 to hit, reach 20 ft., one target. Hit: 21 (2d10 + 10) bludgeoning damage. If the target is a creature, it must succeed on a DC 26 Strength saving throw or be knocked prone.

Breath Weapon (Recharge 5–6). Buttercup uses one of the following breath weapons per head (each head gets its own recharge):

Elemental Breath. Buttercup exhales elemental energy in a 300-foot cone. Each creature in that area must make a DC 25 Dexterity saving throw, taking 84 (13d12) fire damage on a failed save, or half as much damage on a successful one.

Sapping Breath. Buttercup exhales gas in a 300-foot cone. Each creature in that area must make a DC 25 Constitution saving throw. On a failed save, the creature falls unconscious for 1 minute. On a successful save, the creature has disadvantage on attack rolls and saving throws until the end of Buttercup's next turn. An unconscious creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

Change Shape. Buttercup magically transforms into any creature that is Medium or Small, while retaining her game statistics (other than her size). This transformation ends if the dragon is reduced to 0 hit points or uses her action to end it.

Buttercup 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. Buttercup regains spent legendary actions at the start of her turn.

Attack. Buttercup makes one Claw or Tail attack.

Wing Attack (Costs 2 Actions). Buttercup beats her wings. Each creature within 30 feet of her must succeed on a DC 26 Dexterity saving throw or take 17 (2d6 + 10) bludgeoning damage and be knocked prone. Buttercup can then fly up to half her flying speed.

If Buttercup’s Metallic Awakening trait has activated in the last hour, she can use the options below as legendary actions.

Bite. Buttercup makes one Bite attack per head.

Shattering Roar (Costs 2 Actions). Buttercup unleashes a magical roar. Each creature in a 120-foot-radius sphere centered on Buttercup must succeed on a DC 26 Constitution saving throw or take 19 (3d12) thunder damage and be incapacitated until the end of her next turn.