Prior to the Great Change over the world of Space Funeral, Leg Horse was previously known as Prince Horace who ruled over the land of Space Funeral with his brother, Dag. After the Great Change, he was transformed into the sentient mass of several legs.
Leg Horse is first seen fending off Blood Wolves in the wastes and then demands Phillip to join him or die. He will then demand Phillip to take him to the Blood Cavern to see a certain wizard in the cavern since the fate of the world depends on it.
Once Wizard Grum has been found, he demands to talk to the wizard alone. After Phillip speaks to Wizard Grum, who tells Phillip that his journey lies north in the City of Forms, Leg Horse decides that he has his own reasons for travelling there as well and decides that they should travel together.
When Leg Horse finds his old castle in the Ghost Forest, the 20th Century Boy first insults him, which prompts Leg Horse to attack him. After the 20th Century Boy has been defeated, the boy reveals that he was his brother, Dag, who lost his mind after protecting the house waiting for him to return. Dag then tells Leg Horse to avenge him before dying. Leg Horse then tells Phillip to go through the Northern Wastes onto the City of Forms to find the cancer at the heart of the kingdom.
Once at the City of Forms, the party finds Moon and attempts kills her in order to return the world of Space Funeral back to the perfect world it once was.
Leg horse and Phillip then stop the new artists that want to continue moon's work. Afterwards, they are summoned to the scientific land of Earth Birth, where they must get back home and stop the science. He seems to know Aquaman, as before fighting him, he shouts "YOU!"