More details on Mega Evolutions. Mega Diancie receives a big boost to its Speed, as well as boosts to its Attack and Sp. Atk, while experiencing a reduction in its Defense and Sp. Def. Mega Metagross also has a greatly increased Speed stat, with additional increases in its Attack, Defense, Sp. Atk, and Sp. Def, making Mega Metagross primed for both offense and defense.