This particular event occurs after having beaten the Elite Four, unlocked Kiloude City and battled in Kiloude’s Battle Maison (one battle will do). After satisfying these conditions, at the northern portion of Kiloude City, you are allowed to battle your rival once daily.
Rival Battle! Pokemon Trainer Serenas/Calems Party
Whoa, his/her Pokemon are tougher than the Champion’s, slightly, but you should be used to their team now. is the only new Pokemon here and excellent bait for you Poison or Steel-type Pokemon. can be trumped by Dark or Ghosts , while can be punched in the face with Fighting, Bug or Fairy-type moves.
Against , Ice-type Pokemon/moves will make short work of it. The evolutions and your rival’s starter will offer the most resistance, being geared towards you, but you should have plenty of options by now. Again, if you picked , a Flying-type will easily trounce .
After the battle, you’ll receive an Absolite . Absolite allows, obviously, to Mega Evolve, similarly to how your rival’s probably did in the battle. She’ll also mention that Professor Sycamore wants to meet you in Anistar City.
Mega… Mega Ring
Fly, to Anistar City, then go northwest to the sundial. Next to it will be Professor Sycamore. He’ll elaborate on his new theory of Mega Stones. He’ll also mention how some more Mega Stones are hidden throughout the Kalos region: but only really able to be found between 8:00 PM and 9:00 PM - that’s 20:00 and 21:00 per your 3DS clock.