Danjon Kumikyoku

Dispersed around the world, there are several bizarre labyrinths hiding incredible treasures within them. These mysterious places, known as "Dungeons," are said to be the work of Magi, a class of rare magicians, who also help people build their empires by guiding them to a dungeon. Djinns, supernatural beings that rule over the labyrinths, grant successful conquerors access to their immense power and choose them as potential king candidates to rule the world. (myanimelist.net)