Margrave Dain (the Grinning Captain)

Legendary Resistance (2/Day). If Dain fails a saving throw, he can choose to succeed instead.

Amphibious. Dain can breathe air and water.

Dark Devotion. Dain has advantage on saving throws against being charmed or frightened.

Devil’s Sight. Magical darkness doesn’t impede Dain’s darkvision (120 ft.).

Innate Spellcasting (Warlock). Spell save DC 15, +7 to hit with spell attacks.

At will: Eldritch Blast (2 beams, 1d10+4 force each), Mage Hand
2/day each: Armor of Agathys, Misty Step
1/day each: Hunger of Hadar

Multiattack. Dain makes three attacks, using Rapier or Pistol in any combination.

Frost Brand Rapier. Melee Attack Roll: +7, reach 5 ft. Hit: 13 (2d8 + 4) Piercing damage, plus 3 (1d6) Cold damage and Dain has Advantage on the next attack roll he makes with this weapon against that creature before the end of its turn.

While Dain holds the weapon, he has Resistance to Fire damage.

In freezing temperatures, the weapon sheds Bright Light in a 10-foot radius and Dim Light for an additional 10 feet.

When Dain draws this weapon, he can extinguish all nonmagical flames within 30 feet of himself. Once used, this property can’t be used again for 1 hour.

Pistol. Ranged Attack Roll: +7, range 30/90 ft. Hit: 15 (2d10 + 4) Piercing damage.

Captain’s Charm. Wisdom Saving Throw: DC 15, one creature Dain can see within 30 feet. Failure: The target has the Charmed condition until the start of Dain's next turn.

Grasp of the Deep (Recharge 5–6). As a bonus action, shadowy tentacles erupt in a 20-foot square Dain can see within 60 ft. The area is difficult terrain until the start of his next turn. Each creature (other than Dain) in the area when the spell is cast must succeed on a DC 15 Strength save or be Grappled by spectral tentacles until the end of his next turn.

Riposte. Trigger: Dain is hit by a melee attack roll while holding a weapon. Response: Dain adds 3 to its AC against that attack, possibly causing it to miss. On a miss, Dain makes one Rapier attack against the triggering creature if within range.

Dain can take 2 legendary actions, choosing from the options below. Only one legendary action can be used at a time and only at the end of another creature’s turn.

Eldritch Surge. Dain casts Eldritch Blast (one beam). 

Pistol Shot (Costs 2 Actions). Dain makes one pistol attack.

Fathom Pull. One creature within 60 ft. must succeed on a DC 15 Strength save or be pulled up to 30 feet toward Dain.