Tower of Mastery is a tower located in Shalour City. It is currently run by Gurkinn and the successor is Korrina. It is where the player can receive one of Korrina's Lucario and the Mega Ring at the top of the tower after the player defeats Korrina at the Shalour City Gym and then, tested with Lucario against Korrina's another Lucario.
The origins of the Mega Evolution first began when a trainer came to Kalos, accompanied by a Lucario, and found 2 strange stones. One of them reacted to the trainer's Lucario resulting in the first Mega Evolution in history.