Captain Fenrir

Legendary Resistance (3/Day, or 4/Day in Lair). If Fenrir fails a saving throw, he can choose to succeed instead.

Pack Tactics. Fenrir has Advantage on an attack roll against a creature if at least one of his allies is within 5 feet of the creature and the ally doesn’t have the Incapacitated condition.

Shape-Shift. At the start of Fenrir's turn he can shape-shift into a Large monstrosity or a Medium humanoid form. His game statistics, other than his size, are the same in each form. Any equipment he is wearing or carrying is transformed to fit his new size.

Supernatural Restoration. If destroyed by anything other than a Silvered Weapon, Fenrir is revived during the next full moon (1d12 days) with all his hit points. He appears in an unoccupied space within his lair.

Multiattack. Fenrir makes three attacks, using Claw or Moonblade in any combination. He can replace one attack with a Bite attack.

Bite (Monstrosity Form Only). Melee Attack Roll: +9, reach 5 ft. Hit: 11 (1d12 + 5) Piercing damage plus 9 (2d8) Necrotic damage. If the target is a Humanoid, it is subjected to the following effect. Constitution Saving Throw: DC 17. Failure: The target is cursed, and it will become a Werewolf under the DM’s control during the next full moon (1d12 days) unless the curse is removed.

Claw (Monstrosity Form Only). Melee Attack Roll: +9, reach 5 ft. Hit: 15 (3d6 + 5) Slashing damage. If the target is a Large or smaller creature, it has the Grappled condition (escape DC 15), and it has the Restrained condition until the grapple ends.

Moonblade (Any Form). Melee or Ranged Attack Roll: +11, reach 5 ft. or range 20/60 ft. Hit: 11 (1d8 + 7) Slashing damage, plus 7 (2d6) Force damage. Hit or Miss: The Moonblade magically returns to the Fenrir's hand immediately after a ranged attack.

Maneuver (Humanoid Form Only). One ally who can see or hear Fenrir can take a Reaction to move up to half the ally’s Speed without provoking Opportunity Attacks.

Counterattack (Humanoid Form Only). Trigger: Fenrir is hit by an attack roll. Response: Fenrir adds 4 to his AC against that attack, possibly causing it to miss. On a miss, Fenrir can make one Moonblade attack against the attacker.

Legendary Action Uses: 3 (4 in Lair). Immediately after another creature’s turn, Fenrir can expend a use to take one of the following actions. Fenrir regains all expended uses at the start of each of its turns.

Command (Humanoid Form Only). Fenrir chooses one ally he can see. If the ally can see or hear him, it can use its Reaction to make one weapon attack with Advantage. On a hit, the attack deals an extra 10 (3d6) damage.

Feral Strike (Monstrosity Form Only). Fenrir moves up to his Speed without provoking Opportunity Attacks, and he makes one Bite or Claw attack.

Lunar Strike (Any Form). Fenrir uses his Moonblade to cast Moonbeam (DC 15). On later turns he can use a Legendary Action to move the Moonbeam up to 60ft.