Living Blizzard. Absolute Zero is surrounded in a perpetual blizzard which extends ten feet from their body. Creatures inside that radius have a halved DEX score, do half damage with all non-magical attacks and magic weapons, and move 50% slower. Affects those with cold immunities and resistances as well.

Frozen Stiff. Absolute Zero cannot move on their own more than 10 feet, and takes four frost giants to lift.

Spellcasting. Absolute Zero is a 20th-level spellcaster. Its spellcasting ability is Intelligence (spell save DC 30, +20 to hit with spell attacks). Absolute Zero has the following Wizard and Druid spells prepared:

Cantrips (at will): Frostbite, Ray of Frost 

1st level (4 slots): Absorb Elements, Ice Knife

2nd level (3 slots): Snilloc's Snowball Swarm

3rd level (3 slots): Glyph of Warding

4th level (3 slots): Elemental Bane, Fire Shield, Ice Storm

5th level (3 slots): Cone of Cold

6th level (2 slots): Freezing Sphere, Wall of Ice

7th level (2 slots): Prismatic Spray

9th level (1 slot): Prismatic Wall, Storm of Vengeance

Permafrost. Ranged Spell Attack: + 20 to hit, reach 20/60 ft., 40 targets. Hit: 30 (4d10 + 10) cold damage. Everything affected moves at half speed until Absolute Zero is dead or the creature moves over 6 miles away.

Frosty Glance. Ranged Spell Attack: +20 to hit, range 40/120 ft., 1 target. Hit: 100 (10d12 + 60) cold damage.

Summon the Cold. Absolute Zero can use their bonus action to summon 7d10 Ice Mephits, 6d10 Winter Wolves, 5d10 Yetis, 4d10 Frost Giants, 3d10 Abominable Yetis, 2d10 Adult Remorhazes, and 1d10 Ancient White Dragons.

Freezing Wave. Absolute Zero can use their reaction to send a freezing wave out when it is hit by a ranged attack, negating the attack's effect and dealing 30 (4d10 + 10) cold damage as well as 30 (4d10 + 10) bludgeoning damage.

Absolute Zero 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. Absolute Zero regains spent legendary actions at the start of its turn.

Icicle Impale (Costs 1 Action). Absolute Zero summons an ice spike from the ground underneath up to three hostile creatures within 200 ft of them, dealing 50 (6d10 + 20) piercing damage and 15 (2d10 + 5) cold damage.

Iceberg (Costs 2 Actions). Absolute Zero throws an iceberg at a hostile creature within 60 ft of them, dealing 200 (20d12 + 120) bludgeoning damage and 30 (3d12 + 18) cold damage.

Freezing Orb (Costs 3 Actions). Absolute Zero summons a freezing orb above their head, which deals 800 (50d20 + 500) cold damage to anything that gets within 5 feet of it (excluding Absolute Zero and their minions).

Reanimated (Costs 1 Action). When brought to zero hp, Absolute Zero shatters. Only those who have fought Absolute Zero or make a successful DC 30 Wisdom (Perception) check know that Absolute Zero is not actually dead, and will rise again on the sunset of the next day at full hp unless all of their pieces are thrown into the core of a star.