uncommon ce gargantuan acid amphibious dragon 

Perception +35; darkvision, scent (imprecise) 60 feet, true seeing

Languages Aklo, Draconic, Sylvan

Skills Acrobatics +32, Athletics +38, Stealth +34

Str +10 Dex +6 Con +8 Int -1 Wis +7 Cha +8

AC  46; Fort +36, Ref +32, Will +31; +1 status to all saves vs. magic

HP 400, regeneration 15 (deactivated by cold iron); Immunities acid, curse, paralyzed, sleep; Weaknesses cold iron 15

Curse of Death (curse, death, primal) When a creature slays a tarn linnorm, it must succeed at a DC 46 Will save or it can no longer recover Hit Points via any means, such as healing spells, the Medicine skill, or natural healing from rest.

Attack of Opportunity [R] Tail only.

Speed 35 feet, fly 100 feet, swim 80 feet; freedom of movement

Melee [>] jaws +38 (reach 30 feet, magical), Damage 4d12+18 piercing plus tarn linnorm venom

Melee [>] claw +38 (reach 30 feet, agile, magical), Damage 4d8+18 slashing

Melee [>] tail +38 (reach 30 feet, agile, magical), Damage 4d6+18 bludgeoning plus Improved Grab

Primal Innate Spells DC 42; Constant (9th) freedom of movement; (8th) true seeing

Breath Weapon [>>] (acid, evocation, poison, primal) The tarn linnorm can expel either a 120-foot line or a 60-foot cone of acid dealing 20d6 acid damage to creatures within the area (DC 44 basic Reflex save). The acid creates toxic fumes. At the beginning of the linnorm's next turn, those who failed the breath weapon's Reflex save must succeed at a DC 42 Fortitude save or gain sickened 4 from the poisonous fumes. A tarn linnorm can't use Breath Weapon or Overwhelming Breath again for 1d4 rounds.

Constrict [>] 3d6+18 bludgeoning, DC 44

Double Bite [>] The tarn linnorm Strides and then makes a jaws Strike with each of its heads, each against a different target. These attacks count toward the tarn linnorm's multiple attack penalty, and the multiple attack penalty doesn't increase until after the tarn linnorm makes all of these attacks.

Overwhelming Breath [>>>] A tarn linnorm uses its Breath Weapon twice. A creature attempts only one save and can take damage only once. The tarn linnorm can't use Breath Weapon or Overwhelming Breath again for 2d4 rounds.

Tarn Linnorm Venom (acid, injury, poison) Saving Throw DC 44 Fortitude; Maximum Duration 10 rounds; Stage 1 7d6 acid damage and drained 1; Stage 2 11d6 acid damage and drained 2.

Bestiary, page 226.