- "Spitelout, we finally have a Singetail dragon that I can take a real close look at. See if I can find a weakness. Something we can exploit the next time the Flyers attack."
When Hiccup and Toothless go to Storehouse Island to learn more about Singetails, they got separated while fighting one. Hiccup meets Spitelout who came for revenge along with his dragon, Kingstail. Spitelout introduces the Singetails to Hiccup, with the last one being Deathlout who was fighting Toothless. While Hiccup gets to Toothless, Spitelout hits Deathlout with a rock, making the dragon follow him. Spitelout leads the Singetail into a trap, catching it in a net.
Hiccup then suggests studying Deathlout, so he could find anything that might be useful when battling the Dragon Flyers. However, Deathlout makes a distress fire signal and more Singetails come to help him, chasing Hiccup and Spitelout away.
Later, Hiccup comes up with a plan: Deathlout creates another distress fire signal, making all of the Dragon Flyers' Singetails come to his rescue. Hiccup, with the help of Spitelout and Gustav, frees the Singetails from their riders. Then, the Singetails free Deathlout and they all fly away, presumably back to Storehouse Island.
Deathlout is a green Singetail with brown spots on his body. He is covered in many grey scars from battles.
Behaviour and Personality
Like most Singetails, Deathlout is very aggressive, attacking everyone who approaches him.