Strange holes begin appeared in Berk, and taking various sheep with them. A new dragon in the meantime appears, and seems to be targeting Toothless. Toothless doesn't want anyone's help, and Hiccup resorts to desperate needs to keep his friends safe.
- Admiring the Abomination: Ruffnut and Tuffnut love the new dragon that has come to Berk and wreaked destruction.
- Considering this episode aired right after "When Lightning Strikes," in which Hiccup nearly died trying to prove Toothless's innocence, Toothless trying to keep his human away from the Whispering Death makes sense.
- Hiccup's Leap of Faith calls back to the trust building exercise of falling off your dragon, and waiting for them to catch you.
- Cat Scare: Done with a sheep in the tunnels.
- Continuity Nod: Hiccup tries to use dragon nip as a peace offering for the Whispering Death. It doesn't work, but the pile of grass sedates their dragons.
- Didn't Think This Through: Hiccup going off into the tunnels to explore and find the Whispering Death, with only Fishlegs for backup. As they find out, two unarmed Vikings are not that much against a dragon that is willing to kill humans.
- Dude, Not Funny!: In-universe. This is Astrid's reaction to Snotlout reminding Hiccup gleefully that Hiccup is responsible for Toothless's handicap.
- Duel to the Death: This is apparently how a lot of dragon grudges end. Hiccup convinces Toothless not to deliver a fatal blow, however.
- Every Scar Has a Story: The Whispering Death has a scar in the shape of a Night Fury bite. Fishlegs and Hiccup conclude that Toothless and the Whispering Death are bitter rivals engaging in a Duel to the Death.
- Jerkass Has a Point: After Snotlout gives an analysis on how Toothless is at a point of Revenge Before Reason, Hiccup quickly realizes that Toothless is not allowing anyone to help him.
- Leap of Faith: Hiccup jumps off a cliff, trusting that Toothless will come to his senses and save him. Fortunately he was right.
- Noodle Incident: We have no idea how or why Toothless and the Whispering Death became arch enemies, and we never will.
- Revenge Before Reason: Despite having a handicap, Toothless would rather not have anyone help him, including Hiccup.
- Shoo the Dog: Toothless shoots a fireball at Hiccup that deliberately misses, to keep him from following. It doesn't work.
- Take My Hand: Hiccup tries to grab Astrid's hand when he's trapped in the Whispering Death's tunnel, but each time he slips.
- Unknown Rival: Invoked when Snotlout claims that he's Hiccup's archnemesis and thus understands how Toothless thinks.