Hrothgar is a viking of the Knudsen clan. He appears in the season 2 episode "Chapter 4: The Eternal Warriors" and the tie-in novel "Hilda and the White Woff" . The character does not appear in the graphic novels. His name is not revealed in either the animated series, nor the books, but only on the character sheet for the clan.
Hrothgar is a short, muscular man with a white beard, and thick white eyebrows that completely cover his eyes, but otherwise bald. He is the only member of the Knudsen clan to have a hair color other than red.
Hrothgar is the only member of either viking clan who doesn't wear pants, which, according to the character sheet of the Knudsen clan, he eschews.
Not much is known about Hrothgar's personality, other than that, like his fellow vikings, he wants the Medallion of Sigurd to get rid of his fear.
When first seen, Hrothgar, along with the rest of the clan, has been trapped in an endless fight against their rivals, Torgund's clan, over the medallion. Each night the two clans fight, after which the winners take the Medallion, and Sigurd secretly brings the defeated vikings back to life so they can reclaim the medallion.
Hrothgar is seen participating in a battle twice; the first time his clan has the medaillion, and due to the loss of fear they are too reckless to put up a smart fight and are all killed. The following day however, Sigurd revives them with a potion, which also restores their fear and erases their memories of the last battle. With their fear restored, the Knudsen fight much better the second time around and take the medallion from Torgund's clan. They are not seen again after this fight, leaving Hrothgar's fate unknown.