Corrupted Phoenix

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

Blistering Body. Black flames radiate from the Corrupted Phoenix at all times. Anyone within 40 feet of it can feel the heat which intensifies the closer you are to it. If you start your turn within 10 feet of it, you take 14 (2d12) fire damage.

Magic Resistance. The Corrupted Phoenix has advantage on Saving Throws against spells and other magical effects.

Riotous Resurrection. When the Corrupted Phoenix is reduced to 0 Hit Points or less, roll a d20, on a roll of 12 or higher the phoenix is immediately resurrected at 75 Hit Points and may take a turn no matter what point you are at in initiative order. All creatures within 40 feet of the phoenix must then make a DC 15 Dexterity saving throw or take 24 (4d10) fire damage. If the phoenix fails the d20 roll it takes one week to resurrect. Add one to the d20 roll for the phoenix for each resurrection after the first.

Multi-Attack. The Corrupted Phoenix makes two attacks, one with its blinding beak and one with its thrash & snatch. These attacks must be made against different targets.

Blinding Beak. Melee Weapon Attack: +13 to hit, reach 10 ft., one target. Hit: 21 (3d8 + 6) piercing damage and the target must make a DC 18 Constitution Saving Throw or become Blinded until the end of the Phoenix's next turn. 

Thrash & Snatch. Melee Weapon Attack: +13 to hit, reach 30 ft., one target. Hit: 30 (5d8 + 6) slashing damage and the target is Grappled. 

The Phoenix 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 Phoenix regains spent legendary actions at the start of its turn.

Move (Costs 1 Action). The Phoenix may move up to its movement speed without provoking opportunity attacks.

Frightful Presence (Costs 1 Action). Each creature of the Phoenix's choice that is within 120 feet of the Phoenix and aware of it must succeed on a DC 18 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 itself on a success. If a creature's saving throw is successful or the effect ends for it, the creature is immune to the Phoenix's Frightful Presence for the next 24 hours.

Wing Attack (Costs 2 Actions). The Phoenix beats its wings. Each creature within 15 feet of the dragon must succeed on a DC 18 Dexterity saving throw or take 15 (2d6 + 8) fire damage and be knocked prone. The Phoenix can then fly up to half its flying speed.

Fire Breath (Costs 3 Actions). (Recharge 5–6). The Phoenix exhales fire in a 60-foot cone. Each creature in that area must make a DC 18 Dexterity saving throw, taking 63 (18d6) fire damage on a failed save, or half as much damage on a successful one.