Kvasir was created as a peace treaty after the Aesir-Vanir War. He aided Odin, Frey and Heimdall in tracking down Loki after the trickster killed Balder. He deduced that Loki has taken the form of a fish after finding the indentation of a net in the ashes of his fire. The dwarf brothers Fjalar and Gjalar lured him into their cave and killed him.
Magnus Chase dreams of Kvasir helping the gods find Loki and soon after dreams of the god's demise.