The player can obtain the Steelixite by completing the competitive stage available in Week 5 of the event rotation.
The Steelixite was also available as a prize during the Mega Steelix Competitive Stage. This Competitive Stage ran on the Nintendo 3DS version from December 1 to 8, 2015; August 2 to 9, 2016 and September 26 to October 3, 2017. It ran on the Pokémon Shuffle Mobile from August 2 to 9, 2016; and September 26 to October 3, 2017.
The Steelixite enables the following Mega Evolution: