uncommon ce gargantuan dragon 

Perception +30; scent (imprecise) 60 feet, darkvision, true seeing

Languages Aklo, Draconic, Sylvan

Skills Acrobatics +32, Athletics +35

Str +9 Dex +6 Con +8 Int -2 Wis +6 Cha +7

AC  43; Fort +34, Ref +30, Will +26

HP 360, regeneration 15 (deactivated by cold iron); Weaknesses cold iron 15

Curse of the Crooked Cane (curse, primal) When a creature slays a cairn linnorm, it must succeed at a DC 44 Will save or become permanently enfeebled 2. In addition, the victim ages at an accelerated rate, aging 1 year every day, eventually causing it to die of old age if the curse is left untended.

Attack of Opportunity [R] Tail only.

Speed 35 feet, climb 40 feet, fly 100 feet, swim 40 feet; freedom of movement

Melee [>] jaws +35 (magical, reach 25 feet), Damage 3d12+17 piercing plus cairn linnorm venom

Melee [>] claw +35 (agile, magical, reach 25 feet), Damage 3d8+17 slashing

Melee [>] tail +35 (agile, magical, reach 25 feet), Damage 3d10+17 bludgeoning plus

Primal Innate Spells DC 40; Constant (8th) freedom of movement; (7th) true seeing

Improved Grab [F]

Breath Weapon [>>] (acid, evocation, primal) The cairn linnorm expels a 60-foot cone of negative energy–infused acid, dealing 19d6 acid damage to creatures in the area (DC 40 basic Reflex save) The acid also saps the life out of affected creatures. At the beginning of the linnorm's next turn, each creature that failed the Reflex save must succeed at a DC 40 Fortitude save or become drained 1 (drained 2 on a critical failure). The cairn linnorm can't use Breath Weapon again for 1d4 rounds.

Cairn Linnorm Venom (acid, poison) Saving Throw DC 41 Fortitude; Maximum Duration 10 rounds; Stage 1 6d6 acid damage and drained 1 (1 round); Stage 2 8d6 acid damage and drained 2 (1 round)

Bestiary 2, page 166.