Wendigo

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

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

Mimicry. The Wendigo can mimic animal sounds and voices it has heard. A creature that hears the sound can tell if they are imitations with a successful  DC 16 Wisdom (Insight) check.

Piercing Charge. If the Wendigo moves at least 20 ft. straight toward a target, the target must succeed on a DC 15 Dexterity saving throw or take 11 (2d6 + 4) piercing damage and be knocked prone. If the target succeeds, it takes no extra damage and isn't knocked prone. If the target is prone, the Wendigo can make another claw attack against the creature as a bonus action.

Pyrophobia. If the Wendigo takes fire damage it is no longer resistant to bludgeoning, piercing, and slashing from nonmagical attacks at the start of it's next turn.

Regeneration. The Wendigo regains 10 hit points at the start of its turn. If the Wendigo takes fire damage, this trait doesn't function until the start of the Wendigo's next turn. The Wendigo dies only if it starts it's turn with 0 hit points and doesn't regenerate. 

Undead Fortitude.  If damage reduces the Wendigo to 0 hit points, it must make a Constitution saving throw with a DC of 5 + the damage taken, unless the damage is fire or from a critical hit. On a success, the Wendigo drops to 1 hit point instead.

Multiattack.  The Wendigo makes two claw attacks. One attack can be replaced with a throat bite attack or acid reflux, if available. 

Acid Reflux. (Recharge 5-6). The Wendigo vomits acid in a 15-foot cone. Each creature cone must make a DC 14 Dexterity saving throw, taking 15 (3d10) acid damage on a failed save or half as much damage on a successful one.

Throat Bite (Recharge 6) . Melee Weapon attack: +8 to hit, reach 5 ft., 1 target. Hit: 11 (2d6 + 4) piercing damage and make a DC 14 Strength saving throw. On a failed save the target takes an additional 10 (2d10) slashing damage and cannot speak until healed using a spell slot of second level or higher.

Claw. Melee Weapon attack: +8 to hit, reach 5 ft., 1 target. Hit: 7 (1d8 + 4) slashing damage.

Consume. The Wendigo moves towards the closest corpse of a creature that isn't a construct, elemental, or ooze and eats it. For every turn it takes eating the corpse the Wendigo heals 10 (2d6 + 3) hit points and regains one use of Acid Reflux.

Frightful Presence. Each creature of the Wendigo's choice that is within 120 feet of the Wendigo and aware of it must succeed on a DC 16 Wisdom saving throw or become frightened for 1 minute. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. If a creature's saving throw is successful or the effect ends for it, the creature is immune to the Wendigo's Frightful Presence for the next 24 hours.