One Eye is a Sabre-Tooth Driver Dragon who first appears in How to Cheat a Dragon's Curse and later appears in How to Steal a Dragon's Sword. He hates humans in every way when he is first introduced. By some luck, Hiccup manages to have him help find a cure for Fishlegs (which is actually for himself). In the end, One Eye develops a fondness for Hiccup, which is a first for him.
In How to Steal a Dragon's Sword, when Alvin was crowned King of the Wilderwest, One Eye starts to attack him, although he is held back. As Alvin was about to kill him, the dragon rebellion begins, and One Eye joins the Red Rage.