Billow's Sea is a large human-made sea in the Delklands, south of the Sarpland, and wholly within Lobott, spanning the distance from Lobtonne to Asel's Gate at the mouth of the Grey Sea. It was built using the superstrength of Billow the Slave over several years. Its southern shores comprise most of what was once the River Wolf, while the main body of water lies over what was once Arkadia, an ancient kingdom of the Southern Empire.