How to Train Your Dragon Wiki
How to Train Your Dragon Wiki

Hiccup: "I don't think we've ever seen this before."
Fishlegs: "Oh boy! Another deep dweller?!"[src]

The Fathomfin is a gigantic Tidal Class dragon that first appeared in The Serpent's Heir.

Physical Appearance

Titan Wing

According to Richard Hamilton, the only Fathomfin seen thus far in the Franchise is a Leviathan Class dragon, another name for a Tidal Class Titan Wing[1]. This Fathomfin is a gigantic dragon that is mainly blue with dark green spots. It has a large fin lining its back and barnacles covering certain parts of its body, similar to real-life baleen whales.


Expandable Gullet

The Fathomfin has an expandable, pelican-like throat. When expanded, its skin becomes translucent, allowing its rider to see through it and observe their surroundings, similar to a glass bottom boat.[1]

Behavior and Personality

Not much is known about the Fathomfin's personality or behavior, but they are generally peaceful dragons.


Graphic Novels

The Serpent's Heir

When the Dragon Riders were about to reach Nepenthe, Hiccup used his spyglass to observe a Fathomfin surfacing in the distance before commenting on its brief yet mysterious presence. Fishlegs immediately got excited about it and wanted to know more about the new dragon, but Hiccup told him that investigating the situation on Nepenthe was at the moment more important than studying the Fathomfin.

The Fire Tides

According to Richard Hamilton, a Fathomfin helped the Dragon Riders in discovering the remnants of a sunken Viking civilization.


  • The Fathomfin's name was first revealed in a commentary regarding the graphic novel project The Fire Tides.[2]



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