Xixical

Dire Winter. Each creature within 1000ft of the xixical takes 7 (2d6) cold damage at the start of their turn unless they have resistance to cold damage. Water that isn't being held within a sealed container instantly freezes solid. Any creature who spends more than an hour within this radius must make a DC 10 Constitution saving throw each hour or take a level of exhaustion unless resistant to cold. 

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

Magic Weapons. The xixical’s weapon attacks are magical.

Legendary Resistance (3/Day). If the xixical fails a saving throw, it can choose to succeed instead.

Immutable Form. The xixical is immune to any spell or effect that would alter its form.

Regeneration. The xixical regains 30 hit points at the start of its turn. If the xixical takes fire damage or takes damage from a lawful sentient weapon, this trait doesn't function at the start of the xixical's next turn. The troll dies only if it starts its turn with 0 hit points and doesn't regenerate

Innate Spellcasting. The xixical's innate spellcasting ability is Charisma (DC 24). The xixical can innately cast the following spells, requiring no material components:

At will: Divine Word, Cone of cold, Dispel magic (6th level), Dominate monster, Hold person, Greater Invisibility,  Holy Aura (Rather than effecting fiends and undead it effects Celestials and fey, this also gives said celestials and fey the equivalent of the poisoned condition without it actually being the poisoned condition rather than blinding), wall of ice

5/day each: haste, Meteor swarm  

Multi attack. The xixical makes two claw attacks, a bite attack and a stamp attack. If both claw attacks hit the target takes an additional 28 (4d8 + 10) slashing damage and the creature also reduces their maximum hit points by 21 (2d10 + 10), the xixical regains an amount of hit points equal to the amount the creature had their maximum hit points reduced by.  

Bite. Melee Weapon Attack: +19 to hit, reach 15 ft., 1 target. Hit: 24 (4d6 + 10) piercing damage and the target must make a DC 27 Constitution saving throw or take 14 (4d6) cold damage and be under the effects of the slow spell for 1 minute. The creature also reduces their maximum hit points by 21 (2d10 + 10), the xixical regains an amount of hit points equal to the amount the creature had their maximum hit points reduced by.  

Claw. Melee Weapon Attack: +19 to hit, reach 25 ft., 1 target. Hit: 19 (2d8 + 10) slashing damage and the target must make a DC 27 Constitution saving throw or take 14 (4d6) cold damage and be under the effects of the slow spell for 1 minute. The creature also reduces their maximum hit points by 21 (2d10 + 10), the xixical regains an amount of hit points equal to the amount the creature had their maximum hit points reduced by. 

Stamp. Melee Weapon Attack: +19 to hit, reach 15 ft., 1 target. Hit: 36 (4d12 + 10) bludgeoning damage and the target must make a DC 27 Strength saving throw or be knocked prone. The target must make a DC 27 Constitution saving throw or take 14 (4d6) cold damage and be under the effects of the slow spell for 1 minute. The creature also reduces their maximum hit points by 21 (2d10 + 10), the xixical regains an amount of hit points equal to the amount the creature had their maximum hit points reduced by. 

Blizzard Breath (3/Day). The xixical exhales a intense gale of icy cold wind, each creature in a 300ft cone must make a DC 27 Constitutions saving throw or take 42 (12d6) cold damage, or half as much damage on a successful saving throw. If this would kill a creature that creature's body becomes a frozen statue until it thaws.

Summon White Dragon (5/day). The xixical calls forth the wrath of the frozen wastes. An adult white dragon appears within 60ft of the xixical. This dragon is hostile to anything that the xixical is hostile towards. 

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

Attack (Costs 1 Action). The xixical makes a claw attack. 

Glacial barrier (Costs 2 Actions). The xixical gains 20 temperary hit points and a +2 bonus to their armor class, they also automatically succeed any constitution saving throw or check. These benefits last until the start of the xixical's next turn. 

Titan of blizzards (Costs 3 Actions). Each creature within 120ft of the xixical must make a DC 27 Constitution saving throw or take 19 (3d12) cold damage and be pushed 20ft away from the xixical and knocked prone. On a successful saving throw a creature takes half damage and is only pushed 10ft away.