While trying to stabilize the volcano that threatens to destroy Dragon's Edge, the riders discovering troubling evidence of new Hunter activity.
- Aluminum Christmas Trees: The twins helpfully explain that, no, referencing "Mother Nature" would not be anachronistic in their culture.
- The Bus Came Back: The riders return to Melody Island to get some more Deathsong Amber, they discover a very heavily injured Garff. The other Deathsong has gone missing however, courtesy of Krogan.
- Call-Forward: Inferno has a new look. While it is still a solid, non retractable blade, it's now much longer resembling its final form from the movie closer.
- Eureka Moment: When Hiccup sees Meatlug playing with a pair of goggles with Deathsong amber lenses, he and Fishlegs get the idea of combining Deathsong amber with Gronckle iron to create an alloy they could use to plug the volcano.
- Evil Power Vacuum: With the Grimborns dead, Krogan, the mysterious hunter, has taken control of the Dragon Hunters.
- Faux Affably Evil: When one of the dragon-hunters complain about Krogan's methods of retrieving dragons, Krogan asks why he objects. The hunter tells him that using a dragon to hunt other dragons isn't very sportsmanlike, and he considered it cheating. Krogan agrees, and gives the hunter the right to leave if he wants, and when he chooses to do so, Krogan lets him leave. When he waves goodbye to them however, Krogan strikes him down with his axe and tells the others that they will meet the same fate if they leave.
- Get It Over With: Invoked when the twins complain about the volcano not erupting entirely, having to deal with tremors and various false alarms for weeks.
- Know When to Fold 'Em: Hiccup has been fighting the volcano for months. Hiccup is eventually pressured by the others into accepting that it is a futile to keep fighting and with the Dragon Eye destroyed and Viggo defeated, it isn't worth keeping the Edge.
- Time Skip: It's been months since the previous season finale. In the intervening time, Hiccup has made a new model of Inferno and Garff has grown up.