Cryovain

Ice Walk. Cryovain can move across and climb icy surfaces without needing to make an ability check. Additionally, difficult terrain composed of ice or snow doesn't cost it extra movement.

Legendary Resistance (2/Day). If Cryovain fails a saving throw, he can choose to succeed instead. If he does, his speed is halved until the end of his next turn.

Multiattack. Cryovain makes three Rend attacks.

Rend. Melee Weapon Attack: +9 to hit, reach 10 ft., one target. Hit: 12 (2d6 + 5) piercing damage plus 7 (2d6) cold damage.

Cold Breath (Recharge 5–6). Cryovain exhales an icy blast in a 30-foot cone. Each creature in that area must make a DC 17 Constitution saving throw, taking 45 (10d8) cold damage and its speed is halved until the start of next Cryovain's turn on a failed save, or take half as much damage and not have your speed affected.

Icy Grip. Cryovain encases a creature he can see within 60 feet of him in ice. The target must make a DC 17 Strength saving throw. On a failed save, a creature takes 11 (2d10) cold damage and is Restrained. On a successful save, a target takes half as much damage and isn't restrained. On a failed save, the target is Restrained until the ice is destroyed, until Cryovain uses this bonus action again, or until the target or another creature within its reach uses an action to break the ice.

Frost Cataclysm (1/Day). Trigger: Cyovain drops to 100 Hit Points or less. Response: Cryovain roars, causing jagged ice to fall from the ceiling. All creatures within 90 ft must make a DC 17 Constitution Saving Throw. Failure: The creature receives 14 (4d6) cold damage and becomes Prone. Success: The creature receives half as much damage.

Lair Action: The North Wind. On initiative count 20 (losing ties) Cryovain takes his lair action. Each creature besides Cryovain must succeed on a DC 17 Constitution saving throw or take 7 (2d6) and be pushed 10ft.

Lair Action: Blinding Sleet. Driving sleet falls in a 40-foot-high, 20-foot-radius cylinder centered on a point Cryovain can see within 120 feet of it. Each creature in that area must succeed on a DC 17 Constitution saving throw or be Blinded until initiative count 20 on the next round.

Legendary Action Uses: 3. Immediately after another creature's turn, Cryovain can expend a use to take one of the following actions, but he cannot perform the same action in two consecutive turns. Cryovain regains all expended uses at the start of each of its turns.

Pounce. Cryovain moves up to half its speed without provoking opportunity attacks and makes one claw attack.

Reposition. Cryovain can move up to his walking speed in any direction, and any opportunity attacks against him in this movement are made with disadvantage.

Glacial Sweep. Cryovain sweeps his tail in a 10-foot radius (Emanation). Each creature in that area must succeed on a DC 17 Dexterity Saving Throw or take 14 (2d8 + 5) bludgeoning damage and be pushed 10 feet away. Creatures that suffer the Prone condition, make this saving throw with disadvantage.