Toothless

Early years
Toothless presumably grew up in the Alban Hebridges. His parents are unkown and he is the only known Night Fury in the region. As a juvenile dragon, he often accompanied other dragons of the Green Death's nest in cattle raids as air support, confounding the human enemies and freeing captured or pinned dragons. However, information on Toothless in this time period is scarce, and it is unclear if he was a full member of the nest, or if he was merely helping out fellow dragons in distress.

Encounter with Hiccup clan Haddock
Around the time he was reaching maturity, he was hit by Hiccup clan Haddock's newly created dragon capturing weapon, the Mangler, which immobilized him and destroyed his left tail fin. He was subsenquently found by Hiccup, who spared his life and freed him, and proceeded to forge a friendship with him and create a harnessed, human-operated fin prothesis, which allowed Toothless to fly with Hiccup's help.