Bony skull and arms. any piercing, slashing, or bludgeoning damage deal no damage when attacking the skull of arms of the wendigo.

Exposed soul. If the wendigos heart is set on fire, its soul starts to burn and it takes 1d8 fire damage every round at the start of its turn. It becomes enraged and players and enemies can see the past creature in a soul form inside. 

Acid tipped. If the acid wendigo takes acid damage its bite attack and claw attack deal an additional 7 (3d4) acid damage. Its acid spray attack also gains a 15 foot extra range

Cannibalistic nature. If the wendigo hits an enemy with a bite attack the wendigo gains 6 temporary hit points.

Multiattack. The wendigo makes 3 claw attacks and 1 bite attack.

Acid spray. (Recharge 6)  The wendigo sprays a 15 foot cone of acid from its mouth. Any creature in the line must make a DC 15 dexterity saving throw or take 30 (6d10) acid damage.

Claws. Melee Weapon Attack: +8 to hit, reach 10 ft., 1 target. Hit: 7 (2d8 + 3) slashing damage plus 5 (2d4) acid damage.

Antlers. The wendigo charges at a charges at a creature. That creature has to make a DC 17 strength save. On a success they are pushed 15 feet away. On a fail they are pushed 30 feet away.

Enrage. The wendigo screams in frustration, it has advantage on all attacks for 1 minute, after that it takes 1d6 psychic damage.

Bile bite. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 12 (2d10 + 6) piercing damage plus 5 (2d4) acid damage. The target has to make a DC 10 constitution saving throw or become toxicant.

Frightful Presence. Each creature of the wendigos 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 wendigos Frightful Presence for the next 24 hours.

Grapple. The wendigo uses the grapple action as a bonus action.