XP 51,200
CE Huge dragon (cold)
Init +4; Senses dragon senses, snow vision; Perception +32
Aura cold (10 ft., 2d6 cold damage), frightful presence (300 ft., DC 23)

AC 45, touch 8, flat-footed 45 (+4 armor, +29 natural, +4 shield, –2 size); +2 vs. attacks from good creatures
hp 283 (21d12+147)
Fort +19, Ref +12, Will +16; +2 vs. spells from good casters
DR 15/magic; Immune cold, paralysis, sleep; Resist fire 20; SR 26
Weaknesses vulnerability to fire

Speed 30 ft., burrow 30 ft., fly 200 ft. (poor), swim 60 ft.
Melee bite +33 (4d6+19/19–20), 2 claws +32 (2d6+13), 2 wings +30 (1d8+6), tail slap +30 (2d6+19)
Space 15 ft.; Reach 10 ft. (15 ft. with bite)
Special Attacks blizzard, breath weapon (50-ft. cone, DC 29, 20d4 cold), crush, freezing fog (3/day, DC 19)
Spell-Like Abilities (CL 21st, concentration +24)

At will—fog cloud, gust of wind, wall of ice (DC 17)

Spells Known (CL 9th, concentration +12)

4th (4/day)— charm monster (DC 17), dimension door
3rd (7/day)— dispel magic, displacement, lightning bolt (DC 16)
2nd (7/day, 5 remaining)—bull's strength, invisibility, resist energy, web
1st (7/day, 4 remaining)—alarm, mage armor, protection from good, ray of enfeeblement, shield
0 (at will)—acid splash, dancing lights, detect magic, ghost sound, ray of frost, mage hand, mending, message

Before Combat As soon as the PC's are spotted, he casts resist energy (fire), bull's strength, mage armor, protection from good, and shield.  These spell effects are included in his statistics. 

During Combat  He casts displacement immediately before engaging the party.  He flies low over the party and uses his breath weapon, at the same time relying on his frightful presence to weaken his enemies' morale.  If his opponents scatter, he singles out a random opponent in between rounds where he can breathe and makes either a flyby tail slap or a bite so he can snatch at opponent, carry him aloft, breath on him, and drop him from at least 200 feet up.  If confronted with flying foes, he uses gust of wind to send smaller foes reeling and retreats to his lair if he finds their greater mobility is causing him too much trouble. 

Morale If reduced to fewer than 100 hit points, he uses dimension door (if within range) to return to his lair to heal and rethink his tactics based on the combat abilities displayed by his enemies.

Str 37, Dex 10, Con 25, Int 16, Wis 19, Cha 16
Base Atk +21; CMB +36; CMD 46 (50 vs. trip)
Feats Ability Focus (breath weapon), Alertness, Flyby Attack, Improved Critical (bite), Improved Initiative, Improved Natural Attack (bite), Multiattack, Power Attack, Snatch, Vital Strike, Weapon Focus (bite)
Skills Fly +16, Knowledge (Arcana) +27, Knowledge (Geography) +27, Knowledge (History) +27, Perception +32, Sense Motive +32, Spellcraft +27, Stealth+16, Swim+45
Languages Common, Draconic

Blizzard (Su)

An ancient white dragon can use its breath weapon to create a blizzard in the area around it as a standard action. This creates heavy snow conditions in a 50-foot radius for 1 minute, centered on the dragon. This snow slows movement (4 squares of movement per square entered) and limits vision as fog does.

Cold Aura (Su)

An adult white dragon radiates an aura of cold. All creatures within 5 feet of the dragon take 1d6 points of cold damage at the beginning of the dragon's turn. An old dragon's aura extends to 10 feet. An ancient dragon's damage increases to 2d6.

Freezing Fog (Sp)

An old white dragon can use this ability three times per day. It is similar to an acid fog spell but deals cold damage instead of acid damage. It also causes a rime of slippery ice to form on any surface the fog touches, creating the effect of a grease spell. The dragon is immune to the grease effect because of its icewalking ability. This ability is the equivalent of a 6th-level spell.

Ice Shape (Su)

A young white dragon can shape ice and snow at will. This ability functions as stone shape, but only targeting ice and snow, not stone. A white dragon's caster level for this effect is equal to its Hit Dice.

Icewalking (Ex)

This ability works like the spider climb spell, but the surfaces the dragon climbs must be icy. The dragon can move across icy surfaces without penalty and does not need to make Acrobatics checks to run or charge on ice.

Snow Vision (Ex)

A very young white dragon learns to see perfectly well in snowy conditions. A white dragon does not suffer any penalties to Perception checks while in snow.