Archtempered Velkhana

Legendary Resistance (4/Day). If the velkhana fails a saving throw, it can choose to succeed instead.

Magic Resistance. The velkhana has advantage on saving throws against spells and other magical effects.

Rime. An area covered in rime is difficult terrain. Additionally any creature that ends its turn while touching a frost covered area takes 10 (3d6) cold damage and is grappled by the frost (Escape 25).

Multiattack. The velkhana one Bite attack and three Tail attacks.

Bite. Melee Weapon Attack. +16 to hit, reach 15 ft., one target. Hit: 18 (3d6 + 8) piercing damage.

Tail. Melee Weapon Attack. +16 to hit, reach 15 ft., one target. Hit: 17 (2d8 + 8) piercing damage plus 14 (4d6) cold damage.

Breath Weapons (Recharge 5-6). The velkhana uses one of the following breath weapons.

• Cold Breath. The velkhana exhales an icy blast in a 90-foot line that is 5 feet wide. That area is covered in rime for 1 minute and each creature in that line must make a DC 25 Dexterity saving throw, taking 88 (16d10) cold damage on a failed save, or half as much damage on a successful one.

• Hoarfrost Breath. The velkhana exhales an icy blast of hoarfrost in a 60-foot cone. The area is covered in  rime for 1 minute and each creature in that area must make a DC 25 Constitution saving throw, taking 35 (10d6) cold damage on a failed save, or half as much damage on a successful one. Additionally, five 1 foot thick, 10-foot-square walls of ice form within the area and last for 10 minutes. If the wall is formed on a creature's space, the creature is pushed to one side of the wall and must make a DC 25 Dexterity saving throw, taking 35 (10d6) cold damage on a failed save, or half as much damage on a successful one. Each 10-foot section of the wall has 15 AC and 50 hit points, and is vulnerable to fire damage. If damaged to 0 hit points, it leaves a hole filled with freezing air. The first time a creature moves through the air on a turn, it makes a DC 25 Constitution save, taking 17 (5d6) cold damage on a failed save or half as much damage on a successful one

Hoarfrost Armor (2/day). The velkhana coats its body in ice, granting it a +2 bonus to its AC and resistance to bludgeoning, piercing, slashing damage for 1 minute, or until it takes 60 points of damage from a single creature on a turn.

The velkhana 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 velkhana regains spent legendary actions at the start of its turn.

Bite. The velkhana makes one Bite attack.

Wing Attack (costs 2 Actions). The velkhana beats its wings, covering the ground in a 15-foot radius in rime for 1 minute. Each creature within 15 feet of it must succeed on a DC 24 Dexterity saving throw or take 15 (2d6+8) bludgeoning damage and be knocked prone. The velkhana can then fly up to half its flying speed.

Hail Storm (Costs 3 Actions). The velkhana forms six boulder-sized chunks of ice from the water in the air that plummet to the ground at different points within 120 feet of it. Each creature in a 5-foot-radius sphere centered on each point that it chooses must make a DC 22 Dexterity saving throw. A creature takes 13 (3d8) cold damage and 13 (3d8) bludgeoning damage on a failed save, or half as much damage on a successful one. A creature in the area of more than one ice chunk is affected only once.