Corrupted Aspect of the dragon

Amphibious. The dragon can breathe air and water.

Legendary Resistance (3/Day, or 4/Day in Lair). If the dragon fails a saving throw, it can choose to succeed instead.

Aspect of the Dragon At the start of each of it's turns roll a d6 to determine its damage type for it extra damage and has immunity instead of resistance to the damage type until the start of it's next turn

1- cold

2-poison

3-acid

4- lightning

5- fire 

6- necrotic

Corrupted Soul If the dragon is hit with necrotic damage it heals hit points equal to the damage dealt. If the dragon is hit with radiant damage 5 times it's soul is purified and it transforms into an Aspect of the dragon

Weekend Soul: If you use an item to seal or weaken it's soul it losses it's immunity to bludgeoning, piercing, and slashing

Multiattack. The dragon makes three Rend attacks. It can replace one attack with a use of Spellcasting to cast Vampiric touch (level 3 version).

Rend. Melee Attack Roll: +11, reach 10 ft. Hit: 13 (3d6 + 6) Slashing damage plus 4 (2d8) Type determined at start of turn.

Chromatic Breath (Recharge 5–6). Dexterity Saving Throw: DC 18, each creature in a 60-foot-long, 5-foot-wide Line. Failure: 54 (12d8) Damage determined by aspect of the dragon. Success: Half damage.

Spellcasting. The dragon casts one of the following spells, requiring no Material components and using Charisma as the spellcasting ability (spell save DC 17, +9 to hit with spell attacks):

At Will: Detect Magic, Fear, Vampiric Touch (level 3 version)

1/Day Each: Gaseous Form, Blight

Legendary Action Uses: 3 (4 in Lair). Immediately after another creature's turn , the dragon can expend a use to take one of the following actions. The dragon regains all expended uses at the start of each its turns.

2  Elemental torment Dexterity Saving Throw: DC 15, all creatures within 120 feet in the open space of the dragon. Failure: (4d10), the target has vulnerability to the type chosen until the end of the dragons next turn. success half damage only Failure or Success: The dragon can’t take this action again until the start of its next turn.

Elemental burst. Dexterity Saving Throw: DC 17, one creature the dragon can see within 120 feet. Failure: 22 (4d10), the target has vulnerability to the type chosen until the end of it's next turn has until the end of its next turn. Failure or Success: The dragon can’t take this action again until the start of its next turn.

Frightful Presence. The dragon uses Spellcasting to cast Fear. The dragon can’t take this action again until the start of its next turn.

Pounce. The dragon can move up to half its Speed, and it makes one Rend attack.