I received the Voltage Badge and the Thunderbolt TM from Gym Leader Clemont after beating him at the Lumiose Gym, and I used the elevator. I got a Holo Caster message when I left the Prism Tower: Professor Sycamore wanted me to visit Lysandre Cafe, so I headed over there. Once inside the cafe I spoke to Lysandre and I obtained the King's Rock from him. I left Lysandre Cafe afterwards and healed my Pokemon at the Pokemon Center and wandered over to Route 14. As I arrived at Laverre Nature Trail, I met Serena and we battled each other. I used Aerodactyl to beat her Meowstic, then Lucario to defeat her Absol. Finally all that remain was Chesnaught which my Pyroar defeated with Flamethrower attack.