Svaðilfari is the Horse of Hrimthur
Norse Mythology[]
In Norse mythology, Svaðilfari is a stallion horse that was owned by the disguised and unnamed Jötunn who built the walls of Asgard. The giant made a bet with Odin: if he completed the wall within three years, he would take Frigg's hand in marriage. As Odin did not want to lose the bet, he ordered Loki to do whatever it took for the builder to lose the bet.
Loki shape shifted himself into a mare and distracted Svaðilfari far away from the Asgard walls. Nine months later, Loki came back with an eight-legged horse, Sleipnir and gave it to Odin.