Alpha Werewolf

Shapechanger. The Alpha Werewolf can polymorph into a wolf-humanoid hybrid or into a wolf, or back into its true form, which is humanoid as a free action. Its statistics, other than its AC, are the same in each form. Any equipment he is wearing or carrying isn't transformed. It reverts to its true form if it dies.

Keen Hearing and Smell. The Alpha Werewolf has advantage on Wisdom (Perception) checks that rely on hearing or smell.

Cursed Regeneration.Every round, the Alpha Werewolf regenerates 20 HP at the start of its turn unless it has been damaged by a silver weapon within the last round.

Predator. The Alpha Werewolf has advantage on stealth checks if it is in the dark.

Fleet of Foot. The Alpha Werewolf can take the Dash action and the Hide action as a Bonus action.

Frenzy. Once the Alpha Werewolf drops below half HP for the first time, it can make two additional claw attacks when using the Multiattack action for the rest of the encounter.

Savage Attacker. The Alpha Werewolf can reroll damage dice and take the higher of the two rolled.

Bestial Rage. The Alpha Werewolf has advantage on all Strength ability checks and saving throws.

Magic Resistance. The Alpha Werewolf has advantage on saving throws to resist effects of spells.

Multiattack. The Alpha Werewolf uses its Frightful Presence, and then makes one pounce attack and one claw attacks or two claw attacks. Its bite attack can replace any attack.

Pounce. Melee Weapon Attack: +15 to hit, reach 5 ft., one target. Hit 12 (2d6 + 10) bludgeoning damage and the target must make a DC 19 STR saving throw or be knocked Prone and Restrained. A save can be made at the end of the character's turn, as well as each time the Alpha Werewolf takes more than 20 damage in a single attack. Before making this attack, the Alpha Werewolf must move at least 15 ft. in a straight line towards the target.

Frightful Presence. Each creature that is within 120 feet and is aware of the Alpha Werewolf must succeed a DC 19 Wisdom saving throw or take 3d6 psychic damage and be frightened for one minute. A creature can repeat the save at the end of each of its turns, ending the effect on itself on a success, but taking 10 psychic damage on a failure. If a creature's saving throw is successful or the effect ends for it, the creature is immune to the Alpha Werewolf's Frightful Presence for the next 24 hours.

Claw. Melee Weapon Attack: +15 to hit, reach 5 ft., one target. Hit 14 (2d8 + 10) slashing damage and the target must make a DC 19 CON saving throw, taking 14 (4d6) necrotic damage and becoming staggered for one round on a failed save, or half damage and not becoming staggered on a successful save. When staggered, a character has disadvantage on attack rolls and spells have a 25% chance to fail.

Twilight’s Bane. As a bonus action, the Alpha Werewolf extends magical darkness in a 60 ft. radius centered on it. Non-magical and magical lights of 1st level and lower are extinguished within this radius. Dark vision does not penetrate the aura, and creatures within it (excluding the Alpha Werewolf) are considered blinded.

Bite (Recharge 5-6). Melee Weapon Attack: +15 to hit, reach 5 ft., one target. Hit 16 (2d10+10) piercing damage and the target must make a DC 21 Constitution save, taking 28 (8d6) necrotic damage and becoming cursed with Lycanthropy on a failed save, or half damage and resisting the curse on a successful save.

Reactive. The Alpha Werewolf can one additional attack of opportunity per persons' turn. 

The Alpha Werewolf 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 Alpha Werewolf regains spent legendary actions at the start of its turn.

Movement. The Alpha Werewolf can move up to its movement.

Claw Attack.  The Alpha Werewolf makes one claw attack.

Bite Attack. The Alpha Werewolf makes one bite attack.

Shadow Slip. The Alpha Werewolf teleports 30 ft. in any direction by turning into a pure shadow.

Monstrous Howl (Costs 2 Actions). The Alpha Werewolf unleashes a blood-curdling howl. Each creature within 60 feet of it that can hear you must succeed on a DC 19 Wisdom saving throw or take 4d6 psychic damage and become stunned for 1 minute on a failed save. At the end of each of its turns, the target can make another Wisdom saving throw. On a success, the affect ends on the target.