Armor Class 20
Hit Points 333 (18d20 + 144)
Speed 40 ft., fly 80 ft., swim 40 ft., burrow 40 ft.
Saving Throws DEX +6, WIS +7
Skills Perception +13, Stealth +6
Damage Immunities cold
Senses Blindsight 60 ft., Darkvision 120 ft., passive Perception 23
Languages Common, Draconic
Challenge 20
Ice Walk. The dragon 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 (4/Day, or 5/Day in Lair). If the dragon fails a saving throw, it can choose to succeed instead.
Multiattack. The dragon makes three Rend attacks.
Rend. m +14, reach 15 ft. Hit: 17 (2d8 + 8) Slashing damage plus 7 (2d6) Cold damage.
Cold Breath (Recharge 5–6). con DC 22, each creature in a 90-foot Cone. 63 (14d8) Cold damage. Half damage.
Freezing Burst. con DC 20, each creature in a 30-foot-radius Sphere centered on a point the dragon can see within 120 feet. 14 (4d6) Cold damage, and the target's Speed is 0 until the end of the target's next turn. The dragon can't take this action again until the start of its next turn.
Pounce. The dragon moves up to half its Speed, and it makes one Rend attack.
Monster Manual (2024), p. 330