An explosion caused by Sledkin opens up a way into a new realm: the Dark Realm. There, the riders and Sledkin are hunted down by a new dragon, the Glass Caster. Eventually, the dragons and riders get separated. While the riders are forced to work with Sledkin, Thunder must rally the other dragons under him to defeat the Glass Caster and save their friends.
Tropes in this episode include:
- Affably Evil: Despite now being on opposite sides, Linda is still quite nice to the riders.
- Enemy Mine: The riders team up with Sledkin in order to escape the cave the Glass Caster turned into their prison.
- Forced into Evil: Linda is only opposing the riders because she is working for Sledkin. She has no animosity against them.
- Leader Wannabe: Thunder tries to be The Leader to the other dragons throughout the episode, but they are not too impressed by his attempts and largely ignore his commands.
- One Myth to Explain Them All: Jun deduces the Dark Realm is the inspiration for one of the realms from Norse Mythology as the new dragon they encounter looks a lot like a goblin. This further leads her to deduce that the realms from Norse Mythology are based on the Hidden World.
- The Reveal: The discovery of the Dark Realm leads Tom and Jun to discover that the Hidden World forms the basis for the World Tree Yggdrasil from Norse Mythology.
- Super-Hearing: The Glass Caster uses sound reflected from huge crystals to track intruders and prey through its realm.
- Villain Respect: When Tom leaves Sledkin and Linda trapped in the cave the Glass Caster turned into their prison, the former shows some respect for him saying he's not like his mother after all with an impressed smile on her face.
- Wham Episode: Jun deduces the Hidden World forms the basis for the World Tree Yggdrasil from Norse Mythology meaning there are still two realms left undiscovered.
- World Tree: In-universe, the Hidden World forms the basis for the World Tree Yggdrasil from Norse Mythology.
- Xanatos Gambit: In order to escape their makeshift prison, Sledkin teams up with the riders and plans to make a run for it after escaping while the riders fight the Glass Caster. At first, it seems she pulls a Batman Gambit as she explains to Linda that Tom wouldn't leave them trapped due to being The Hero. However, Tom does leave them trapped, much to Sledkin's suprise. When Linda asks her what to do next, she tells her to shut up and pulls out a piece of Dragoncite, which she uses off-screen to cut their way out of their prison and makes a run for it while the riders fight the Glass Caster, just as originally planned.
