Dragon, White Great Wyrm (CR 20)

Gargantuan Dragon (Cold)
Alignment: Always Chaotic Evil
Initiative: +0; Senses: blindsense 60 ft., darkvision120 ft., low-light vision, and keen senses
Languages: Draconic

AC: 41 (-4 size, +35 natural), touch 6, flat-footed 41
Hit Dice: 36d12+288 (522 hp); DR: 20/magic
Fort +28, Ref +20, Will +24
Speed: 60 ft., fly 250 ft. (poor), swim 60 ft., burrow 30 ft.
Space: 20 ft./15 ft. (20 ft. with bite)
Base Attack +36; Grapple +61
Attack: 1 Bite +45, 2 claws +40, 2 wings +40, 1 Tail Slap +40, 1 crush +40, 1 Tail sweep +40 melee; Breath +45 ranged
Damage: 1 bite 4d6+13, 2 claws 2d8+6, 2 wings 2d6+6, 1 tail slap 2d8+19, 1 crush 4d6+19, 1 tail sweep 2d6+19, Breath weapon 20d6 (31)
Special Attacks/Actions: Breath weapon, fear (DC 32), SR 27
Abilities: Str 37, Dex 10, Con 27, Int 18, Wis 19, Cha 18
Special Qualities: Cold subtype, icewalking, Fog cloud, Gust of wind, Freezing fog, Wall of ice, Control weather, CL 13
Feats: #Feats: 13
Skills: Skill points: 150
Advancement: 37+ HD (Gargantuan)
Climate/Terrain: Any cold land and underground
Organization: Solitary, pair, or family (1-2 and 2-5 offspring)
Treasure/Possessions: Double Standard

Source: Monster Manual

Breath Weapon (Su): A white dragon has one type of breath weapon, a cone of cold (12d6 cold damage, Reflex save for half damage DC 36). Using a breath weapon is a standard action. Once a dragon breathes, it can't breathe again until 1d4 rounds later. A blast from a breath weapon always starts at the dragon's mouth and extends in a direction of the dragon's choice.

Frightful Presence (Ex): A young adult or older dragon can unsettle foes with its mere presence. The ability takes effect automatically whenever the dragon attacks, charges, or flies overhead. Creatures within a radius of 360 feet are subject to the effect if they have fewer HD than the dragon (36).

A potentially affected creature that succeeds at a Will save (DC 32) remains immune to that dragon's frightful presence for one day. On a failure, creatures with 4 or fewer HD become panicked for 4d6 rounds and those with 5 or more HD become shaken for 4d6 rounds.

Dragons ignore the frightful presence of other dragons.

Cold Subtype

A creature with the cold subtype has immunity to cold. It has vulnerability to fire, which means it takes half again as much (+50%) damage as normal from fire, regardless of whether a saving throw is allowed, or if the save is a success or failure.