One Eye is a Sabre-Tooth Driver Dragon, a type of dragon that doesn't hibernate, unlike all of the others. This has given them the nickname of "Ever-Greens", not after their scale colour (which is completely white), but after the type of coniferous tree that remain green and active all year round, including the coldest of winters. He appears in How to Cheat a Dragon's Curse and 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 heldack. As Alvin was about to kill him, the dragon rebellion begins, and One Eye joins the Red Rage.