Childe Tartaglia

Foul Legacy (Mythic Trait; Recharges after a Short or Long Rest).  If Childe Tartaglia is reduced to 0 hit points, he doesn’t die or fall unconscious. Instead, he regains 60 hit points. Additionally, he enters the Foul Legacy Transformation.

Riptide. When a creature is hit by Childe Tartaglia's Water Blade and Water Arrow attack, they are affected by riptide until the end of their next turn. When a creature with riptide is dealt damage, they and other creatures that are not Childe Tartaglia within 5 ft take an additional 1d6 slashing damage. When a creature with riptide is reduced to 0 hit points, the riptide will erupt dealing 1d12 slashing damage to creatures within 5 ft and applying riptide to them. 

Water Burst. Childe targets a creature that he can see within 20 ft. the creature must make a DC 12 Dexterity saving throw and takes 10 (2d8) bludgeoning damage as on a failure, half damage on a success, as water bursts from the ground.

Water Blade. Melee Weapon Attack: +6 to hit, reach 5 ft., 1 target. Hit: 15 (2d12) Slashing damage. 

Water Arrow. RangedWeapon Attack: +6 to hit, range 30/60 ft., 1 target. Hit: 12 (2d8 + 5) Bludgoning damage.

Drowned Whale (Recharge 5–6). Childe summons a Whale made of water that breaches from the ground and lands in front of him. Creatures in a line 40 ft long and 10 ft wide take 20 (3d12) bludgeoning damage and must make a DC 15 Strength saving throw or be knocked prone.

Child Tartaglia gains access to the following legendary actions when he falls below half health or if his Mythic trait is active. He uses them as actions.

Electric Torrent (Recharge 3–6). Childe Tartaglia makes 2 Water Arrow attacks. Each attack made with this action deals an additional 1d8 lightning damage.

Lightning Blade Dance (Recharge 4–6). Childe Tartaglia makes 3 Water Blade attacks. Each attack made with this action deals an additional 1d6 lightning damage.

Thundering Strike (Recharge 5–6). Childe Tartaglia calls down lightning to strike his foes. a creature that he can see must make a DC 14 Dexterity saving throw or take 20 (3d12) lightning damage on a failure, half damage on a success. 

While Childe Tartaglia is under the effects of the Foul Legacy Transformation, he gains the following abilities. 

Dark Transformation. Childe Tartaglia gains a flying speed (hover) equal to his walking speed and becomes large. While he is hovering he gains immunity from being knocked prone and a +3 bonus to AC.

Unlimited Power. Childe Tartaglia's legendary actions lose their recharge feature.

Grand Reckoning (2/day). As an action, Childe Tartaglia causes 4 runic circles to appear. They have a 20 ft radius and appear 30 ft from each other, forming a square with their center's. At the start of Child Tartaglia's next turn, the circles will erupt, dealing 50 Bludgeoning Damage to creatures within the circles. If a creature is within 2 circles they are dealt this damage twice.