Aspect of Castor

Amphibuous. Castor can breathe air and water.

Blood Frenzy. Castor has advantage on melee attack rolls against any creature that doesn’t have all its hit points.

Discorporation. When Castor drops to 0 hit points or dies, his body is destroyed but his essense lingers traveling back into its domain in Submarina where it fashions a new body for itself in 2d100 days. When the new body is complete, Castor regains all his hit points and becomes active again.

Keen Smell. Castor has advantage on Wisdom (Perception) checks that rely on smell.

Legendary Resistance (5/Day). If Castor fails a saving throw, he can choose to succeed instead.

Dominator of the Sea. As an action, Castor can issue a magical command at any aquatic beast within 120 feet of him that he can see, using a limited telepathy. A creature above CR 5 can make a DC 25 Wisdom saving throw, resisting the command on a successful save.

Innate Spellcasting. Aspect of Castor's innate spellcasting ability is Charisma (spell save DC 24, +16 to hit with spell attacks). Castor can cast the following spells, requiring no material components:

At will: shape water, ice knife (as a 7th level spell), rime's binding ice (as a 5th level spell), sleet storm

3/day each: wall of ice, control water, ice storm (as a 7th level spell), freezing sphere, cone of cold

Special Equipment. Semour carries a magical trident which requires attunement, named Trident of Disasters. It is a +3 trident. While attuned to the trident he can, as an action, cast tsunami, control weather or earthquake at will, once per day each, requiring no material components (save DC 19).

Multiattack. Aspect of Castor makes four melee weapon attacks, only one of which can be a Harpoon Hand attack.

Trident of Disasters. Melee Weapon Attack: +20 to hit, reach 10 ft. or range 20/60 ft., one target. Hit: 20 (2d8 + 11) piercing damage plus 28 (8d6) cold damage. During a storm, when thrown wherever the trident lands it's as if the call lightning spell was cast at that point (Save DC 19).

Harpoon Hand. Melee Weapon Attack: +17 to hit, reach 10 ft., one target. Hit: 15 (2d6 + 8) piercing damage plus 18 (4d8) lightning damage, and the target must make a DC 26 Constitution saving throw or be paralyzed for 1 minute. The target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

Hydro Breath (Recharge 5-6). Castor exhales water in a 60-foot line that is 5 feet wide. Each creature in that area must make a DC 26 Dexterity saving throw, taking 76 (17d8) magical bludgeoning damage on a failed save, or half as much damage on a successful one. Being underwater imposes disadvantage on creatures attempting to succeed the saving throw.

Oceanic Titan (Recharges on a Short or Long rest). For 1 minute, Castor magically doubles in size, along with anything he is wearing or carrying. While enlarged, Castor is Huge, his Strength-based weapon attacks deal an extra die of damage, his reach increases by 5 feet, and he makes Strength checks and Strength saving throws with advantage. If he stands under running water or is submerged in water Oceanic Titan has no time limit. This trait activates on its own if he stands in running water such as rain, for at least 1d4 rounds. If he is submurged in water it activates automatically. He revurts back his regular size if he dies.

Aspect of Castor 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. Aspect of Castor regains spent legendary actions at the start of its turn.

Trident of Dissaters. Castor makes one Trident of Dissaters attack.

Intimidate. Castor rolls a Charisma (Intimidation) check contested by a Wisdom check from a creature he can see within 10 feet of him. If the targets check is less than Castor's, they become frightened off him until the end of his next turn.

Jet Thrust (Costs 2 Action). Castor moves his speed and makes one Trident of Disasters attack. If the attack hits the creature must succeed on a DC 26 Strength saving throw or be knocked prone.