Articuno

Flyby. The Articuno doesn't provoke opportunity attacks when it flies out of an enemy's reach.

Snowstorm. The Articuno's space is heavily obscured. This effect ends if the Articuno is incapacitated or dies.

Frigid Blast. The Articuno releases a freezing blast. The blast reaches an area of 35x35 feet, centered on the Articuno, and freezes any item in the radius that isn't being worn or carried. Every creature in the blast radius (except the Articuno) must succeed on a DC 15 Constitution saving throw or become blinded, deafened, and paralyzed for one minute. Regardless of whether the target succeeds or fails the throw, it's speed is reduced by half until the target finishes a long rest. A creature who's speed is reduced to less than five in this way gains dissadvatage on attack rolls until it finshes a long rest.

Beak. Melee Weapon Attack: +5 to hit, reach 5 ft., 1 target. Hit: 18 (3d6 + 9) Slashing damage.

Hailstorm. Ranged Weapon Attack: +5 to hit, range 20/60 ft.,  up to 6 targets. Hit: 30 (10d6) cold damage.

Icicle. Melee Weapon Attack: +4 to hit, reach 10 ft., 1 target. Hit: 10 (2d6+4) cold damage.

If an attack made by the Articuno hits at least one target, the Articuno can take a bonus action immediately after. It can take only one of each bonus action each round.

Frigid Wind. The Articuno flaps its wings, causing a gust of wind to blow throw the area. Each creature within 15 feet of the Articuno must succed on a DC 15 Dexterity saving thow or be pushed back 10 feet and fall prone.

Icy Terrain. The Articuno causes snow to coat the ground, powering up its attacks. For one minute, each creature within 100 feet of the Articuno with resitance or immunity to cold damage loses that resistance or immunity. Cold damage also deals an extra 2d4 damage until the effects wear off. Additionally, any creature that falls prone in the area slides back 20 feet.

Powder Snow. The articuno heals 2d4+4 Hit Points. It can't use this bonus action if it has taken any fire damage since it's last turn.

Evasive Flight. The Articuno moves up to half its speed.

The Articuno can take 3 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 Articuno regains spent legendary actions at the start of its turn

Icy Defense (Costs 1 Actions). The Articuno gains a +2 bonus to AC until the start of its next turn.

Icicle Shard (Costs 2 Actions). The Articuno makes two Icicle attacks. They must both target the same creature, even if the first attack drops the target to 0 HP.

Ancient Power (Costs 3 Actions). Until the end of it's next turn, the Articuno gains a +2 bonus to attack rolls, and a +3 bonus to AC.