Argynvost, The Returned (Raventide)

Aura of Fear. Any creature that starts its turn within 120 feet of Argynvost must make a DC 18 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.

Ice Stride. Difficult terrain composed of ice or snow doesn’t cost Argynvost extra movement.

Legendary Resistance (3/day). If Argynvost fails a saving throw, it can choose to succeed instead.

Turn Resistance. Argynvost has Advantage on saving throws against any effect that turns undead.

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.

Wight Sight. Argynvost can see clearly in areas obscured by falling snow, flurries, snow storms, and fog.

Multiattack. Argynvost makes three attacks: one with its bite and two with its claws.

Bite. Melee Weapon Attack: +12 to hit, reach 10 ft., one target. Hit: 19 (2d10 + 8) peircing damage and the target is grappled (escape DC 21) if it is Medium or smaller. Until this grapple ends, Argynvost can't use its breath attack and can bite only the grappled creature; and has advantage on attack rolls to do so.

Claw. Melee Weapon Attack: +12 to hit, reach 5 ft., one target. Hit: 15 (2d6 + 8) slashing damage.

Tail. Melee Weapon Attack: +12 to hit, reach 15 ft., up to two targets that are adjacent to each other. Hit: 17 (2d8 + 8) bludgeoning damage. If the target is a Medium or smaller creature, it must succeed on a DC 18 Constitution saving throw or gain the prone condition.

Breath Attack (Recharge 5-6). Argynvost breathes a 60 ft cone of ice and necrotic energy. Creatures within the cone must make a DC 18 Dexterity saving throw, taking 35 (10d6) cold damage and 35 (10d6) necrotic damage on a failed save, or only half as much on a successful one. Creatures that fail the saving throw by 5 or more become partially incased in ice and 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’s Swift Wings. While flying 60 feet or more above the ground, Argynvost can Dash as a bonus action once on its turn.

Argynvost can take 3 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.

Bite. Argynvost makes one bite attack.

Claw. Argynvost makes one claw attack.

Detect. Argynvost makes a Wisdom (Perception) check.

Wing Attack (Costs 3 Actions). Argynvost beats its wings. Each creature within 10 feet of Argynvost must succeed on a DC 18 Dexterity saving throw, or take 18 (3d6 + 8) bludgeoning damage. A creature that fails the save by 5 or more gains the prone condition. Argynvost can then fly up to half of its flying speed.