«Ruby Palace» (紅玉宮(こうぎょくきゅう), Kougyoku-kyū?) was a red palace on the 100th and final floor of Aincrad in Sword Art Online. If the game had proceeded as planned, this would have been the place where the Clearers who had reached the topmost floor alive would have fought against the final boss, Heathcliff, beating the game if they were victorious.