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From Pathfinder Bestiary 2, which isn't enabled.

Fjord Linnorm

CREATURE 16
UNCOMMONGARGANTUANAMPHIBIOUSCHAOTICDRAGONEVIL

Fjord linnorms make their homes in damp caves behind ice-cold waterfalls in the river-veined coastal reaches of the north. While they may appear graceful as they swim up the fjords for which they're named, they are as vile as any other of their species and take pleasures in capsizing river boats before gobbling up their terrified crews.

Perception +28; darkvision, scent (imprecise) 60 feet, truesight 60 feet
Languages Aklo, Draconic, Fey
Skills Acrobatics +27, Athletics +33, Stealth +29
Str +9, Dex +5, Con +8, Int -3, Wis +6, Cha +7
Constant Spells

A constant spell affects the monster without the monster needing to cast it, and its duration is unlimited. If a constant spell gets counteracted, the monster can reactivate it by spending the normal spellcasting actions the spell requires.

AC 40; Fort +30, Ref +28, Will +24; +1 status to all saves vs. magic
HP 315, regeneration 10 (deactivated by cold iron); Immunities cold, curse, paralyzed, sleep; Weaknesses cold iron 15
+1 Status to All Saves vs. Magic
Regeneration 10 (Deactivated by Cold Iron)

This monster regains the listed number of Hit Points each round at the beginning of its turn. Its Dying condition never increases beyond Dying 3 as long as its regeneration is active. However, if it takes damage of a type listed in the regeneration entry, its regeneration deactivates until the end of its next turn. Deactivate the regeneration before applying any damage of a listed type, since that damage might kill the monster by bringing it to Dying 4.

Attack of Opportunity (Tail Only)

Tail only

Trigger A creature within the monster's reach uses a manipulate action or a move action, makes a ranged attack, or leaves a square during a move action it's using.
Effect The monster attempts a melee Strike against the triggering creature. If the attack is a critical hit and the trigger was a manipulate action, the monster disrupts that action. This Strike doesn't count toward the monster's multiple attack penalty, and its multiple attack penalty doesn't apply to this Strike.

Curse of Stolen Breath (curse, primal, water)

When a creature slays a fjord linnorm, it must succeed at a DC 41 Will save or become unable to ever breathe underwater (either via a natural ability or a spell such as water breathing). In addition, the victim can hold its breath only half as long as normal, and whenever it holds its breath it becomes Sickened 2.

Speed 35 feet, fly 75 feet, swim 50 feet
Melee Jaws +33 (magical, reach 20, unarmed), Damage 3d12+17 piercing plus Fjord Linnorm Venom
Melee Claw +33 (agile, magical, reach 20, unarmed), Damage 3d10+17 slashing
Melee Tail +33 (agile, magical, reach 25), Damage 3d6+15 bludgeoning plus Improved Grab
Primal Innate Spells DC 37, attack +27; Constant (7th) Freedom of Movement; Constant (6th) True Seeing
Breath Weapon (cold, primal)

The fjord linnorm expels a 120-foot line of icy bile, dealing 17d6 cold damage to creatures within the area (DC 37 basic Reflex save). Any creature that fails its save is covered by the ice, which freezes and fuses with the creature's skin, giving it a –10-foot penalty to Speed. A creature can Escape or Force Open the ice (DC 34) to free itself; otherwise, the ice remains for 1 minute.

The fjord linnorm can't use Breath Weapon again for 1d4 rounds.

Fjord Linnorm Venom (cold, poison)
Saving Throw DC 37 Fortitude
Maximum Duration 10 rounds
Stage 1 4d6 cold damage and Clumsy 1 (1 round)
Stage 2 6d6 cold damage and Clumsy 2 (1 round)
Improved Grab

Trigger The monster's last action was a successful Strike that lists Improved Grab in its damage entry, or the monster has a creature Grabbed or Restrained
Effect If used after a Strike, the monster attempts to Grapple the creature using the body part it attacked with as a free action. This attempt neither applies nor counts toward the creature's multiple attack penalty.

The monster can instead use Improved Grab as an action and choose one creature it's grabbing or restraining with an appendage that has Improved Grab to automatically extend that condition to the end of the monster's next turn.

Pathfinder Bestiary 2OGL