To ensure the future survival of Mala's tribe, she and Hiccup must deposit a newly laid Eruptodon egg into the deadly Grand Volcano so it will hatch.
Tropes:
- Are You Pondering What I'm Pondering?: Hiccup and Fishlegs are in sync at the start of the episode, but get thrown off their game when it comes time to deliver the egg. They get back on track by the end.
- Convection, Schmonvection: Played with. On the one hand, the Defenders note that the Eruptodon saliva helps thermally insulate their armor from the heat of the magma, while on the other, Throk and Astrid use Hiccup's diving bell to create a heatproof boat that can get them to the cage. Nevermind the fact that the bell is formerly one of Gobber's Smelting Cauldrons, and should have sunk straight into the magma at the first opportunity.
- Deus Exit Machina: The lava-proof Eruptodon is worn out from laying the egg and can't deliver it, forcing Hiccup, Fishlegs, and Mala to do so. It recovers in time to save Throk at the end.
- Not Evil, Just Misunderstood: The volcanic Night Terrors were trying to take the Eruptodon egg to its nesting place, not that their sinister appearance and aggressive tactics would tell you that.
- Red Eyes, Take Warning: Unlike the known Night Terrors, the ones in the volcano have glowing red eyes and are extremely territorial to boot. And then subverted when it turns out that they usually don't work alongside humans, and they were just trying to save the Eruptodon egg by escorting it to the heart of the volcano.
