Rúrik Sveinnsson Svarthæð (ルーリック・スヴェインソン・スヴァルトヘイズ), mostly referred by his first name Rúrik, is a Nótt Álfur and the first prince of the country of Svarthæð. The first son of King Sveinn, he has a contrasting personality with his siblings Sigurð, Helga and Críe, harboring dark thoughts in his being.
Rúrik does not appear in the anime adaptation.
Slightly shorter than his younger brother, Rúrik is good-looking and tall young man with a very similar appearance to Sigurð, but with a more elegant, serious and dark expression. He uses square glasses and is normally seen in formal garments.
Rúrik is the first prince of Svarthæð, the country of the Nótt Álfur. Not much is known prior to his appearance in the story, but it's known that, at some point, the only woman he ever loved was raped and killed by Álfur, which eventually lead him to despise all those that lived in peace and carefree.
An accomplished soldier and statesman, he is expected to be the successor of King Sveinn since Sigurð is considered immature to be the heir to the throne. His brother Sigurð is always wary of Rúrik's actions with women since he knows that Rúrik, behind her facade, in reality is a jerk. After being confined in his country, when he first appears in Ygvar, he boldly molests her sister Helga until Naoya casually interrupts him.
Rúrik meets with the chiefs of the Retrospective Faction, who oppose the Reconciliatory Faction of his father, with the purpose of allying with them to incite chaos and create an opportunity to return to Svartálfaheimr. Unbeknownst to him, his father Sveinn had plans to make Sigurð his successor since he saw behind Rúrik's pretence.
As part of his plan, Rúrik orders Kisulora, a woman who is loyal to him, to seduce division commander Killeffer from Ygvar and to manipulate him in order to facilitate a coup d'état against Mercelída's government in order to take control of Yggdrasill. As part of his plan, he poisons his father in order to assume the command of Svarthæð. But his plan is foiled by his father who, aware of Rúrik's true nature, had made Sigurð his successor beforehand. On top of that, his plan required the collaboration of Kirik, who instead acts against it.
After taking control of the Nótt Álfur army, when Sigurð goes to stop him at Yggdrasill, it turns out that Rúrik didn't really care if the plans succeeded or not. His true intention was to disappear from Álfaheimr, so he uses Yggdrasill's power to either return to Svartálfaheimr or fall into Múspellheimr, Helheim or the void between realms, taking the heads of the Retrospective Faction with him. Rúrik's objective was to drag the world into a maelstrom of chaos and war as payback for what the world had done to him when he lost his only beloved.
He shows a cold and calculated demeanor, but in reality it's a facade. An incident from his past in which the only woman he ever loved was raped and killed by Álfur set him in a path to seek revenge against the world, making him despise everyone and himself, to the point of even trying to kill his father and not caring whether or not he lived as long as he could cause some chaos to the world. Sigurð describes Rúrik as a jerk with a pair of hands that moves faster than his mouth, making him worried about Rotte's well-being since, as Sigurð puts it, at least Sigurð flirts before making a move. This is evidenced when upon meeting his sister, Rúrik molests her and when he orders Kisulora, who loves him, to seduce another man with the incentive of having sex with her despite not loving her.
Despite being an skilled soldier and statesman, he cares for nothing, even of his own life. He easily betrays the Retrospective Faction when he no longer needs them. His cruel and twisted personality, which he believes is well hidden, is in fact well known by his father and brother. In the end, he is a sad man that no longer wishes to live in a world that took her beloved and only keeps on living with the intention to exact whatever revenge he can on the world.