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The Selkidomus is a beast demon that lives in the seas around the Boiling Isles. It is stated by Eda that it is a peaceful creature as long as nobody provokes it; or if it's a mother Selkidomus, threaten to harm its baby.


An infant Selkidomus.

The Selkidomus is a giant seal-like sea monster, as its flippers and its stance when it's on land resemble those of real-life pinnipeds or seals. Like real-life seals, the Selkidomus has four flippers; except that its front flippers are bigger and has three digits on each one, while the hind flippers are smaller and have only two digits. Unlike real-life seals, the Selkidomus has a long tail that ends in a whale-like fluke, with a small spine on the tips of its fluke. The color of its skin is grayish-purple with a light-gray underbelly, while its nose and forehead are a darker shade of purple. It has black eyes, and pink coloration that surrounds the eyes. It has three webbed shark-like dorsal fins on its body: a small one in its neck, a big one on its back, and another small one on its tail. The Selkidomus also has aquatic plants growing, looping and covering its neck, back, and sides of its mouth.

Juvenile selkidomus resemble their parent, albeit smaller and with rounder proportions. They have a single dorsal fin, a sapling on their head, and two leaf bristles protruding from their muzzle.


According to Eda, the Selkidomus is a peaceful creature, and it will only attack if provoked. However, if the Selkidomus is a mother, it will attack anything or anyone that she perceives as a threat to her infant. But if one is able to prove to the mother that they are not a threat to her baby, or lucky enough to be recognized as not a threat at all, the mother Selkidomus will calm down. Additionally, a mother Selkidomus has a sense of gratitude to those who helped her defend herself and her infant. And in return for helping her, a Selkidomus mother will reward anyone with selkigris, which is highly prized.


The Selkidomus is first seen on a "wanted" poster on Greg's List, with a reward of 1,000,000 snails on it, when Luz suggests that a way to boost her, Eda, Lilith, and King's confidence is by taking on the biggest bounty they can find. However, Eda refuses because they need to lie low while her powers are still weak, and what they need is a much easier bounty. After Luz overhears Eda saying that she is spending the money only on food that she can eat, she feels guilty and decides that to make it up to Eda. Luz, along with King, joins a crew to hunt for the Selkidomus.

Later, at the Simmering Shoals, where the Selkidomus was last sighted, the Selkidomus appears and begins attacking the crew by launching spikes at them. Luz, using her ice magic by redirecting it, places it in a position, so it can easily be captured, and using her plant magic to restrain it, successfully captures the Selkidomus. However, it breaks free and escapes when a mysterious pirate bombards their ship and steals the reward money.

After Luz and the pirate, revealed to be Eda, confront the Golden Guard on an island, Eda demands to know why Emperor Belos wants the Selkidomus dead. The Golden Guard replies that he is simply following orders, and soon gives Luz and Eda a compromise: Kill the Selkidomus, or King will be drowned in the Boiling Sea. With no alternative solutions left, Luz agrees, much to Eda's chagrin; the latter follows her and she reveals that she is doing this to make up for everything that happened to Eda.

Luz engages the Selkidomus and fights it, but the beast soon overwhelms her. While she tries killing it, Eda stops her, reassuring her that she brought joy into her life. They then discover that the Selkidomus has a child, and together, they come up with a plan to save themselves without hurting it. Using plant and light magic, Luz and Eda fool the Golden Guard into thinking that they killed the Selkidomus, prompting him to release King and fly off. Upon his departure, Eda warns the Selkidomus that it needs to leave the area, as it isn't safe. As a reward for protecting it and its child, the Selkidomus vomits up golden selkigris, which, according to Eda, is worth a fortune.[1]

In "Knock, Knock, Knockin' on Hooty's Door", the picture of a Selkidomus appears on Hooty's demonology board among other beast type demons.

In "Eclipse Lake", in the Emperor's Castle, a book that Belos left open reveals that the scales of a Selkidomus are one of the items needed for a "Grimwalker".

Powers and abilities

  • Spine shooting: When threatened, the Selkidomus can inflate its neck into a balloon, revealing plenty of spines on it, and then ejecting every spine in every direction, hitting any potential target.
  • Selkigris production: The Selkidomus can barf up a substance known as selkigris, which is noted to be valuable.


Behind the scenes

Early development

According to concept art for the Selkidomus, the creature initially had a more serpentine appearance, with yellow skin, spines, and a webbed tail, as well as a secondary seal-like hide.[2]

Name and basis

The Selkiedomus may be based on the Selkie, a Celtic-Norse mythological creature that shapeshifts between human and seal forms by donning and shedding their enchanted sealskin. This is supported by the creature originally having the skin of a pinniped draped around its body in its original design.[2] "Selkie" is the Scottish term for "seal", thus combined with the suffix "-domus", meaning "house" or "ruling" in Latin, "selkiedomus" roughly means "ruler of seals", befitting the creature. Their ability to produce selkigris also alludes to a sperm whale's ability to produce ambergris.




ve Characters
Main Characters Luz NocedaEda ClawthorneKingHooty
Recurring characters Willow ParkGus PorterAmity BlightOwlbertLilith ClawthorneHunter
Emperor's Coven Members Emperor BelosKikimoraWarden WrathCoven GuardFlora D'splora
Coven Heads Raine WhispersDariusEberwolfTerra SnapdragonAdrian Graye Vernworth
Hexside Students and Staff Principal BumpPrincipal FaustEdric BlightEmira BlightMattholomuleBoschaProfessor HermonculusBraxasVineyJerboBarcusBoCatUsurperAmeliaSkaraEileenMoon girl
Glandus Students BriaGavinAngmar
Boiling Isles Citizens Tinella NosaKatyaWarden WrathTibblesAnimal ControlDottieMerchantAlador BlightOdalia BlightPerry PorterPinietMortonRoselleSaltyGilbert and Harvey ParkGwendolyn ClawthorneDell ClawthorneAmberDerwinMalphasMaster WortlopSeverineSteve
Monsters and Demons Bat QueenAdegastSnagglebackGrometheusSlitherbeastThe InspectorFairyJean-LucSelkidomusOwl BeastVeeBatric
Fictional Characters AzuraHecateGildersnake
Other Characters Camila NocedaInner WillowJacob HopkinsInner BelosCollectorTarakBill