The player can obtain the Latiasite by passing Level 50 on a Mega Latias Escalation Battle in Weeks 8 and 9 of the event rotation.
The Latiasite was also available as a prize during the Mega Latias Escalation Battles prior to the event rotation system. This Escalation Battle ran on the Nintendo 3DS version from September 28 to October 12, 2015; January 31 to February 14, 2017; and October 24 to November 7, 2017. It ran on the Pokémon Shuffle Mobile from November 24 to December 8, 2015; January 31 to February 14, 2017; and October 24 to November 7, 2017.
The Latiasite enables the following Mega Evolution:
Data for Latiasite exists within the code of Pokémon X and Y, despite the Mega Stone not being officially introduced until Omega Ruby and Alpha Sapphire, allowing it to be transferred to and used in X and Y. It shares this trait with the Latiosite.