Team Flare showdown | Walkthrough Pokemon X/Y Guide

After leaving the gym You receive a message from Lysandre, the leader of the Team Flare, head (preferably use the HM Fly) back to Luminose and into Lysandre café, talk to the people inside, get the password, and try to activate the hidden entrance in the far side of the room. In the underground base, keep defeating grunts until You get an elevator key. Once You get it, use the elevator to get down. Repeat the process and proceed once You get to the third floor. After the battles head out, and get to Geosynge town, there, heat north-west into yet another secret base, keep pushing forward, and get to Lysandre. Take care of more minions, then prepare for a special battle with either Xerneas or Yvetal (depending on which version You have). The legendary Pokemon can be caught only here and now, and will make a great addition to Your team. Catch it and be done with Lysandre (whom You will battle after the legendary encounter). Get back to Anistar and head south, to Road 18.