Gorstaag

Gorstaag is one of Ruffnut and Tuffnut's uncles.

Insomnia
It is noted by Ruffnut and Tuffnut that their uncle, Gorstaag, had insomnia for 27 years. His symptoms were: uncontrollable euphoria, mood swings, complete catatonia (which he describes as "a rash around your neck that extends down your back to your buttocks"), lack of coordonation and paranoia.

Dragons: Race to the Edge, Season 4
Gorstaag is briefly mentioned by the twins when the Dragon Riders had insomnia during the midnight sun.