Disobeying Hiccup, the twins follow a retiring Eruptodon to its final resting place, Vanaheim, and learn why no human has ever gone there before.
- Due to the Dead: Although we don't see a funeral in process, the Sentinels clearly treat the dying with respect and care and entomb the remains of each dragon with their own kind.
- Elephant Graveyard: Vanaheim is an island where dragons who reach their golden years or become fatally ill venture to where they live out their final days.
- Food Fight: The riders try covering themselves and their dragons in fruit in order to mask their scent against the sentinels. In their efforts to do so, they end up in a food fight. It gets the job done at least.
- Foreshadowing: Hiccup tells Mala at one point that he would be pretty sad if he had to say goodbye to Toothless for good, which eventually happens in How To Train Your Dragon The Hidden World.
- Herbivores Are Friendly: Averted. The Sentinels eat fruit and are anything but friendly.
- No Listening Skills: Hiccup gives the twins "the look" as he says that Vanaheim must not be disturbed by humans, knowing fully well that they would do just that if it was not spelled out to them. They don't get the hint.
- Our Gargoyles Rock: The Sentinels are a group of gargoyle-like dragons that watch over Vanaheim (metaphorically speaking since they're blind) that manage the island and make sure that its purpose is fulfilled, even if that means keeping its inhabitants from leaving.
- Taught by Experience: The Sentinels spend their entire lives caring for ailing dragons of all kinds, and thus know exactly how to perfectly counter anything any of them can throw at them. The only exception is Toothless. There have never been any Night Furies in Vanaheim.
- Wham Shot: Near the end of the episode, the shot of Vanaheim zooms out to reveal that the entire island is built around the fossilized skeleton of a Bewilderbeast.