The Atlantis usurpation was a plan by Orm to seize the throne of Atlantis.
History[]
Orm tricked Aquaman into leaving Atlantis to go to the surface world, where assassins waited to kill him. Orm then seized the throne and began an attack on the "surface-dwellers" with a weapon designed to melt the polar ice caps. He was stopped by the Justice League, and Aquaman was reinstated as the rightful monarch.