|Friends/Allies||Gustav, Snotlout Jorgenson, Hiccup Horrendous Haddock III, Hookfang, Toothless|
|First Appearence||The Flight Stuff|
|Last Appearence||The Flight Stuff|
Fanghook has the characteristics of a normal Monstrous Nightmare, although he is seemingly kinder and gentler than Hookfang, although still having the brashness from him. He is seen to be easily intimidated by Hookfang when they first met and more compassionate to Gustav than Hookfang is to Snotlout most of the time. Although meeting Gustav for only a day, the dragon and boy quickly bond together enough for Gustav to ride him, making the dragon somewhat protective of him. He has an undeniably strong sense of loyalty towards his rider, as he merely waited for Gustav to call him, after he was 'released'.
Fanghook first appeared when Gustav was looking for his own dragon. After rejecting the Terrible Terror and the Deadly Nadder, he found Fanghook chasing boars, picking him because Snotlout described the Monstrous Nightmare as "the most lethal dragon in the known world." However, due to Snotlout's "training," Gustav's relationship with Fanghook was like Snotlout and Hookfang's.
Gustav decides to head to Outcast Island after overhearing about the scouting mission from Trader Johan. The two easily get captured in Dagur's new trap, but are soon released by Hiccup. They then work with Snotlout and Hookfang to save Hiccup and Toothless.
The next day, Gustav releases Fanghook back into the forest. After Hiccup and Snotlout leave, Gustav calls his dragon and the two continue training together in secret.
Having the average Nightmare abilities, Fanghook was able to learn some skills in one day.
- Communication Skills: He was able to learn two types of orders from his owner that are very useful, in just one day.
- Evasive Manners: Like most Nightmares, Fanghook is quite agile and flexible, as he was able to dodge the arrows of the Berserkers and Outcasts with ease.
- Fire It Up:Gustav's battle cry, which he in ordered for Fanghook to flame up. Unlike Hookfang, Fanghook obeys this command.
Gustav Larson: When Gustav was denied membership to the Academy, he went into the forests in order to find and train his own Dragon. After rejecting a Nadder and some Terrible Terrors, he stumbled upon Fanghook. Though they had a rocky start and weren't the best team, they still care greatly for one another. At the end of The Flight Stuff, Gustav 'released' Fanghook back into the wild, though they kept training in secret.
Hookfang: Upon the first meeting, Hookfang showed a certain disdain and hostality towards Fanghook, succesfully intimidating Fanghook.
- Fanghook's first appearance was in Episode 12 "The Flight Stuff."
- Fanghook's name is a play-on the name Hookfang (Snotlout's dragon).
- Fanghook's coloration is similar to the Monstrous Nightmare Astrid trained on Outcast Island when she was pretending to be Heather, and may be the same dragon.
- Fanghook is the only known dragon on Berk to be training outside the Dragon Academy.
- Fanghook is shown to be smaller than Hookfang, and may well be younger or simply smaller.