Aura of Fear. Any creature that starts its turn within 120 feet of Argynvost must make a DC 20 Wisdom saving throw. On a failed save, the creature is Frightened for 1 minute. A creature can repeat the saving throw at the start 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 (after 1 minute or otherwise), the creature is immune to Argynvost’s Aura of Fear for the next 24 hours. 

Legendary Resistance (2/day). If Argynvost fails a saving throw, it can choose to succeed instead.

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

Multiattack. Argynvost makes three attacks: one with its Bite and two with its Claws.

Bite. Melee Weapon Attack: +13 to hit, reach 10 ft., one creature. Hit: 21 (3d8 + 8) peircing damage and the target is grappled (escape DC 21) if it is Large or smaller. At the start of each of Argynvost’s turns, a grappled target takes 21 (3d8 + 8) peircing damage. Argynvost cannot use its bite attack or it’s breath attack while it has a creature grappled in this way, Argynvost may grapple only a single creature at a time with its bite attack.

Claw. Melee Weapon Attack: +13 to hit, reach 10 ft., one creature. Hit: 19 (3d6 + 8) slashing damage.

Tail Sweep (Recharge 5-6). Argynvost sweeps its tail in a wide arc around itself. All creatures within 15 feet of Argynvost must make a DC 18 Dexterity saving throw, taking 18 (3d6 + 8) bludgeoning damage on a failed save and only half (1/2) as much damage on a successful save. Creatures that fail the save are pushed back 10 feet. Creatures that fail the save by 5 or more are knocked Prone.

Breath Attack (Recharge 5-6). Argynvost breathes a 60 ft cone of ice. All creatures within the cone must make a DC 18 Dexterity saving throw, taking 35 (10d6) cold damage and35 (10d6) necrotic damage on a failed save, and only half (1/2) as much on a successful save. Creatures that fail the saving throw by 5 or more are Restrained until the end of their next turn, or until they take 15 points of damage. While a creature is Restrained in this way, Argynvost’s successful claw and bite attacks made against it are critical hits.

Death Eater. Argynvost makes one Bite attack against an undead within reach that is Large or smaller. If the attack is successful and the damage dealt is enough to destroy the target; Argynvost immediately consumes the undead target and regains hit points equal to half 1(/2) of the damage dealt.

Argynvost can take 2 legendary actions, choosing from the options below. Only one action option can be used at a time and only at the end of another creature’s turn. Argynvost regains spent legendary actions at the start of its turn.

Claw (Costs 1 Action). Argynvost makes one claw attack.

Detect (Costs 1 Action). Argynvost makes a Wisdom (perception) check.

Wing Attack (Costs 2 Actions). Argynvost beats its wings, throwing debris into the area around it. Each creature within 15 feet of Argynvost must succeed on a DC 18 Dexterity saving throw or take 21 (3d8 + 8) bludgeoning damage. A creature that fails the save by 5 or more is knocked Prone. Argynvost can then fly up to half (1/2) of its flying speed.