Black Ascendant Dragonborn

Amphibious. The dragonborn can breathe air and water.

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

Multiattack. The dragonborn makes three Greataxe attacks. It can replace one attack with either an Acidic Rend attack or a use of Spellcasting to cast Melf’s Acid Arrow (level 4 version).

Greataxe. Melee Attack Roll: +16, reach 10 ft. Hit: 23 (2d12 + 10) Slashing damage plus 9 (2d8) Acid damage.

Acidic Rend. Melee Attack Roll: +11, reach 10 ft. Hit: 27 (4d10 + 5) Acid damage. If the target is a creature, it takes an additional 9 (2d8) Acid damage at the start of each of its turns, and it receives a -3 penalty to its AC. A creature can only receive one instance of this AC penalty at a time. If the creature or one of its allies takes an action to remove the acid, the damage ceases and the AC penalty is removed.

Acid Breath (Recharge 5–6). Dexterity Saving Throw: DC 21, each creature in a 90-foot-long, 10-foot-wide Line. Failure: 53 (12d8) Acid damage. Success: Half damage.

Spellcasting. The dragonborn casts one of the following spells, requiring no Material components and using Charisma as the spellcasting ability (spell save DC 19, +11 to hit with spell attacks):

At Will: Detect Magic, Fear, Melf’s Acid Arrow (level 4 version)
3/Day Each: Create Undead, Destructive Wave, Vitriolic Sphere (level 7 version)

Beat Wings. Strength Saving Throw: DC 22, each creature in a 15-foot emanation. Failure: 9 (2d8) Acid damage and pushed 15 feet directly away from the dragonborn. Success: Half damage only.

Tail Attack. Melee Attack Roll: +14, reach 10 ft. Hit: 19 (2d10+8) Bludgeoning damage, and the creature is Grappled (Escape DC 22). While a creature is Grappled in this way, it is also Restrained and this attack automatically succeeds against it.

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

Cloud of Insects. Dexterity Saving Throw: DC 19, one creature the dragonborn can see within 120 feet. Failure: 33 (6d10) Poison damage, and the target has Disadvantage on saving throws to maintain Concentration until the end of its next turn. Failure or Success: The dragonborn can’t take this action again until the start of its next turn.

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

Pounce. The dragonborn moves up to half its Speed, and it makes one Greataxe or Acidic Rend attack.