The Border Sea is an evil location and place in The Keys to the Kingdom series. It was an ocean previously under the rule of the gluttonous Lady Wednesday. It was the third demense that Arthur gained control of as the Rightful Heir. After Lady Wednesday turned into a leviathan/large whale known as Drowned Wednesday, caused by the treachery of Superior Saturday. In Lord Sunday, the Sea is revealed to be destroyed by a wave of Nothing. However, it is now very likely remade by the New Architect.