Kaiju, Yarthoon

This immense pale blue worm raises one end of its body like a serpent, its many-toothed maw opening amid a ring of glowing eyes.

Yarthoon CR 25

XP 1,638,400
CN Colossal magical beast (air, kaiju)
Init +13; Senses low-light vision, mistsight, see in darkness, tremorsense 300 ft.; Perception +28


AC 44, touch 12, flat-footed 34 (+9 Dex, +1 dodge, +32 natural, –8 size)
hp 565 (29d10+406); fast healing 30
Fort +30, Ref +25, Will +19
Defensive Abilities ferocity, recovery; DR 20/epic; Immune ability damage, ability drain, cold, death effects, disease, energy drain, fear; Resist acid 30, electricity 30, fire 30, negative energy 30, sonic 30


Speed 60 ft., burrow 100 ft., fly 100 ft. (average), swim 100 ft.
Melee 2 bites +39 (4d6+27/19–20 plus 4d6 cold and grab), slam +39 (4d8+27/19–20 plus 4d6 cold and staggering strike)
Space 30 ft.; Reach 30 ft.
Special Attacks clinging frost, eye beams, fast swallow, freezing mist, hurl foe, penetrating cold, swallow whole (6d6 bludgeoning and 6d6 cold damage, AC 26, 56 hp), swift bite


Str 46, Dex 29, Con 38, Int 3, Wis 26, Cha 21
Base Atk +29; CMB +55 (+59 overrun); CMD 75 (77 vs. overrun, can’t be tripped)
Feats Critical Focus, Dodge, Flyby Attack, Greater Overrun, Improved Critical (bite, slam), Improved Initiative, Improved Iron Will, Improved Overrun, Improved Vital Strike, Iron Will, Power Attack, Staggering Critical, Vital Strike, Wingover
Skills Fly +32, Perception +28, Swim +26; Racial Modifiers +16 Perception
Languages Auran (can’t speak)
SQ massive, no breath, powerful blows (bite, slam), starflight


Clinging Frost (Su)

Whenever a creature takes cold damage from Yarthoon (including from her freezing mist), the creature becomes encrusted with a layer of clinging frost for 1 round. The duration of this clinging frost stacks with multiple instances of cold damage from Yarthoon. As long as a creature has at least 1 round of clinging frost remaining, it takes a –2 penalty on all Reflex saving throws and Dexterity-based skill checks. As long as a creature has at least 2 rounds of clinging frost remaining, it is staggered. Freedom of movement negates the effects of clinging frost, and if a creature activates a fire-based supernatural ability on its turn, it reduces the number of rounds remaining by 1d4. Creatures with the fire subtype, the heat ability, or any similar ability to shed significant warmth are immune to clinging frost.

Eye Beams (Su)

Once every 4 rounds as a standard action, Yarthoon can emit several beams of freezing energy from her eyes. When Yarthoon uses this attack, she can choose to fire all of the beams in one direction to create a single line 1,200 feet long, or she can instead fire eight separate beams as ranged touch attacks with a range of 1,200 feet. If she chooses to fire them in a line, all creatures within the area of effect take 20d6 points of cold damage (Reflex DC 38 half). If she fires the beams as ranged touch attacks, she has a +30 attack bonus but can target a single creature with no more than two eye beams at a time (though she can fire the beams in any direction to attack multiple targets in range). A single eye beam deals 8d6 points of cold damage on a hit (no save). The save DC for the line-based attack is Constitution-based.

Freezing Mist (Su)

Once per day as a swift action, Yarthoon can exhale a cloud of freezing mist, filling a 200-foot-radius sphere surrounding her. This mist obscures vision as per obscuring mist and persists for 10 rounds, and is not dispersed by moderate wind. A strong wind (21+ mph) disperses the mist in 2d4 rounds, while fireball, flame strike, or similar spells burn away the mist in the spell’s area. Any creature within the area of the mist when Yarthoon creates it takes 8d6 points of cold damage (Reflex DC 38 half). A creature that begins its turn within the mist takes 4d6 points of cold damage (no save) at the start of its turn. The save DC is Constitution-based.

Penetrating Cold (Su)

When Yarthoon deals cold damage, the damage ignores the first 30 points of cold resistance the target has.

Staggering Strike (Ex)

If Yarthoon hits a Gargantuan or smaller foe that’s standing on the ground with her slam attack, the target struck must succeed at a DC 42 Reflex save or be knocked prone and become staggered for 1d6 rounds. If she hits a Gargantuan or smaller flying foe, the creature is staggered for 1d6 rounds and must succeed at a DC 42 Fly check or lose 30 feet of altitude (a winged flying creature loses 60 feet of altitude instead; this replaces the normal rule for being attacked while flying for winged creatures). A Colossal creature struck by Yarthoon’s slam must succeed at a DC 42 Reflex save to resist being staggered for 1 round, but is not knocked prone or forced to lose altitude. The save DC is Strength-based.

Starflight (Su)

Yarthoon can survive in the void of outer space. She flies through space at incredible speeds, but generally only does so to travel between the moon and the world below when her attention is caught or her curiosity piqued. It takes Yarthoon only 2d4 hours to travel from the moon to the world below. If she were to travel to a more distant point in the same solar system, she requires only 3d6 days to make the journey, while trips beyond this range generally take her 3d6 weeks.

Swift Bite (Ex)

Yarthoon strikes with astonishing speed when she attacks with her bite. Whenever Yarthoon makes a bite attack on her turn, she can attack two times, either as a standard action to bite twice, or as part of a full attack to bite two times in addition to making one slam attack. She can make any number of attacks of opportunity with her bite attack, but does not get to bite more than once when she does so.


Environment any cold (the world’s moon or outer space)
Organization solitary (unique)
Treasure incidental

Yarthoon is among the least powerful of the kaiju, yet even she is of staggering size and capable of unleashing devastation on an apocalyptic scale. Known as the Moon Grub to kaiju scholars, Yarthoon does indeed dwell upon the moon itself, where she spends much of her time in a frozen reach of ice and snow, created, in part, by her presence and the effects of her freezing breath over the course of centuries. (Note that although Yarthoon’s exhalations fill the region with freezing mist, the Moon Grub herself has no need to breathe and can exist comfortably in the vacuum of space.) Were Yarthoon content to remain upon the moon, there would be little known about the frozen kaiju; unfortunately, the larger world her home orbits is a constant fascination for her. Indeed, certain events have been known to specifically attract Yarthoon’s attention, whether they’re intentional calls such as powerful rituals led by apocalyptic cultists, or accidental lures that occur when powerful effects of magical cold occur. The exact nature of these attractions varies, and even the most learned scholars argue over what exactly it is that draws Yarthoon to visit the world. None, however, dispute the devastation Yarthoon unleashes, if unintentionally, when she visits the world. Unlike many kaiju, Yarthoon seems not to purposefully seek out civilizations to destroy, but her immense size and her freezing breath wreak havoc nonetheless. Fortunately, Yarthoon’s visits to the world typically last for only a few days before she slithers off into the sky like an eel swimming through water to return to her den on the moon.

Yarthoon has a complex relationship with Mogaru, the Final King. Often, Mogaru’s devastation on a region is enough to lure Yarthoon down from the moon, in which case she often clashes with the more powerful kaiju. Likewise, Mogaru’s ability to sense kaiju often results in him coming to investigate a region that Yarthoon has decided to visit. Yet the two kaiju never seem willing to finish a fight against the other, and rather than deliver a death blow when the chance rises, each seems content to let the other flee. The one thing that seems to unite the two kaiju is their shared hatred of Lord Varklops, and the two kaiju have teamed up several times to drive off the three-headed fiend more than once.

Although Yarthoon is the least powerful of the known kaiju, the Moon Grub has been remarkably resilient. Time and time again, Yarthoon has returned after suffering what seemed to be a complete defeat, at either the hands of powerful heroes or the claws and fangs of fellow kaiju. Scholars of these immense monsters have theorized that Yarthoon may not be a unique creature, and that in its hidden lair on the moon, multiple Moon Grubs writhe and dream. Others posit that Yarthoon is but the larval stage of a kaiju, and that while only one may live at any time, numerous other eggs lie in a hidden crèche on the moon, waiting to hatch and release replacement Moon Grubs as needed.

Yarthoon is 250 feet long from head to tail and weighs 14,000 tons.

Section 15: Copyright Notice

Pathfinder Roleplaying Game Bestiary 6 © 2017, Paizo Inc.; Authors: Robert Brookes, Benjamin Bruck, John Compton, Paris Crenshaw, Adam Daigle, Crystal Frasier, James Jacobs, Thurston Hillman, Tim Hitchcock, Brandon Hodge, Jason Keeley, Isabelle Lee, Jason Nelson, Tim Nightengale, F. Wesley Schneider, David Schwartz, Mark Seifter, Todd Stewart, Josh Vogt, and Linda Zayas-Palmer.

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