Wendigo

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

Faltering Mimicry. The Wendigo has learned to mimic the voices of those it has heard cry out in fear. While the Wendigo cannot speak or understand language it can mimic cries for help in the common tongue to attract potential prey. This language is imperfect and unnatural. A creature can determine the voice it hears is strange with a successful DC 15 Wisdom check. A creature proficient in (Performance) automatically succeeds on recognizing the voice to be suspect.

Darkvision. The Wendigo has darkvision to 150 Ft.

Unnatural Hunger. The Wendigo is ravenous and seeks fresh meat of almost any form, preferring that of humanoids. When a creature is wounded the wendigo can almost unerringly track the scent of blood.

Dark Resilience. A Wendigo can only be truly killed by burning its heart in fire. When its hp reaches 0 the Wendigo falls unconscious and is effectively dead. However If its heart is not removed and burned or its whole body set aflame for at least an hour, it will awaken after 5 hours and slowly regenerate its Hp and all bodily damage over a period of 1d4 days. Even if its body is destroyed it will regenerate after 1d4 Days around its heart if it is unburned.

Ravenous Growth. A Wendigo left unchecked will seek flesh above all. With every corpse the wendigo consumes its body absorbs the raw components and grows by approximately an inch of added body mass. This growth is accelerated by consuming particularly large or powerful foes. 

Slow Recovery. If the Wendigo is knocked Prone it requires all of its movement to stand up instead of half.

Multiattack. The Wendigo makes two attacks: One flailing strike and one Claw attack

Flailing Strike. Melee Weapon Attack: +5 to hit, reach 10 ft., one target. Hit: 5 (1d6 + 2) bludgeoning damage. On a hit a target must make a DC 14 Strength saving throw or be knocked 10 ft away and Prone

Claw. Melee Weapon Attack: +4 to hit, reach 10 ft., one target. Hit: 6 (1d6 + 4) slashing damage.

Antler Lock. The Wendigo Rears back and slams its antlers into the character who last made a successful melee attack against it and attempts to lock them into a grapple. Melee Weapon Attack: reach 10 ft., one target. Make an Grapple check. The winner of the check successfully subjects the loser to the Grappled condition.

On beginning its turn and successfully having another creature grappled the wendigo may make a free Flailing Strike as a bonus action against the target it has grappled. The target automatically fails the save against being knocked away and prone when grappled in the lock. If however the wendigo begins its turn grappled by another character. That character may use a reaction to attempt to twist the wendigo's antlers and knock it down. Make another opposed check. If the wendigo succeeds nothing happens and the wendigo is still considered Grappled as it continues its turn. If the other contestant succeeds the Wendigo is knocked prone, the Grapple ends and the Wendigo may not use the Multiattack action on its current turn. The Wendigo requires all of its movement to recover from the Prone

The Wendigo can take 2 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 Wendigo regains spent legendary actions at the start of its turn.

Flailing Strike. The Wendigo makes one flailing strike attack.

Unnatural Howl. The Wendigo emits a fearsome shriek. Each creature within 60 feet of the Wendigo that can hear the roar must succeed on a DC 12 Wisdom saving throw or be frightened of the wendigo until the end of the Wendigo's next turn.