Captain Dahl

Brute. A melee weapon deals one extra die of its damage when the captain hits with it (included in the attack).

Regeneration. Captain Dahl regains 10 hit points at the start of its turn. If he takes fire or radiant damage, this trait doesn’t function at the start of the captain's next turn. The captain's body is destroyed only if it starts its turn with 0 hit points and doesn’t regenerate.

Rejuvenation. When the captain's body is destroyed, its soul lingers. After 24 hours, the soul inhabits and animates another corpse on the same plane of existence and regains all its hit points. While the soul is bodiless, a wish spell can be used to force the soul to go to the afterlife and not return.

Typhoon. The captain wields the legendary trident Typhoon, which has a +3 bonus to attack and damage rolls, deals an additional 4 (1d8) cold damage, and can cast the following spells (Spell Attack +8, Spell Save DC 16)
At will: frostbite (3d6)
1/day each: tidal wave, control water, maelstrom,tsunami 

Turn Immunity. The Captain is immune to effects that turn undead.

Vengeful Tracker. The captain knows the distance to and direction of any creature against which it seeks revenge, even if the creature and the captain are on different planes of existence. If the creature being tracked by the captain dies, the captain knows.

Multiattack. The captain makes three melee attacks with Typhoon or two ranged attacks with Typhoon.

Typhoon. Melee or Ranged Weapon Attack: +12 to hit, reach 5 ft. and range 20/60 ft., one target. Hit: 11 (2d6 + 8) piercing damage, or 13 (2d8 + 8) piercing damage if used with two hands to make a melee attack, plus 4 (1d8) cold damage. If the target is a creature against which the captain has sworn vengeance, the target takes an extra 14 (4d6) piercing damage

Captain Dahl 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 Captain regains spent legendary actions at the start of its turn.

Trident. The captain makes an attack with Typhoon

Icy Waters. The captain casts Frostbite from Typhoon

All Hands on Deck! (Costs 2 Actions). Two ghosts appear in an unoccupied space within 30 ft. of the captain. The ghosts take their turns immediately and then disappear.

Fury of the Sea (Costs 3 Actions). The captain casts a spell from typhoon.