Back when Mega Sableye was first revealed, and we didn't even know its ability, one among you suggested that it and Mega Diancie might get the same ability based on the fact that they were both based on gems.
Whoever you are, since I don't remember, you're a freaking PSYCHIC.
Magic Bounce Mega Diancie, huh? Holy shit this thing suddenly looks insane. Sick defenses so you can't touch it offensively, Magic Bounce so you can't touch it defensively. Even with Diancie's base stats this would be really solid, but with 100 extra stat points? Holy shit we might be seeing Shaymin-S all over again. Absolutely shitty base form, so Gamefreak tries to improve it drastically and ends up going well into overkill territory.