Starting today, you can get your hands on a set of mega stones in Pokémon Sun and/or Moon via mystery gift. This batch includes a Beedrillite, a Mawilite, an Audinite, and a Medichamite. The serial code required for these stones is: INTIMIDATE. There is no end date for these. Also, if you haven't gotten your hands on Mewtwo's mega stones yet, you can still get them, as those are a permanent event. The code for those 2 stones is M2DESCENT. Happy mega evolving!