“"You were chosen to be a movie star, correct? Isn't it your duty to be ever beautiful? Everything beautiful should stay that way forever. I would end the world in an instant so that beauty never fades. I can't stand the thought of the world becoming uglier."”
Lysandre makes his first appearance in this game. You first encounter him in Lumiose City, where he is first introduced as the head of Lysandre Labs. He discusses with Diantha about her acting career and eternal beauty. Much later, after you beat the 5th Gym Leader, Clemont. He tells you about Xerneas or Yveltal (depending on your game), and the ultimate weapon.
After you beat the 7th Gym, it's revealed that Lysandre is the leader of Team Flare, and you go to Lysandre Labs in Lumiose City to attempt to stop him. While there, you battle him once and he retreats underground.
Later, at the Team Flare Secret HQ under Geosenge Town, you battle him once more, to stall time. Later, after catching the game's ledgendary Pokémon, you fight him for a third time. In this battle, he uses a Mega Gyarados. After battling him one final time, he fires a severely weakened version of the Ultimate Weapon. Him and the rest of Team Flare are trapped in the rubble of the HQ, and he can be presumed to be killed.
Pokémon Ultra Sun and Ultra Moon
He returns in this game, as a member of Team Rainbow Rocket. This wasn't the Lysandre from Pokémon X and Y, and instead came from a universe where the Ultimate Weapon successfully fired. When you fight him, he uses a Xerneas (Ultra Sun) or Yveltal (Ultra Moon), in addition to his previous Pokémon. After being defeated, he wonders what would've happened if a person like the main character in USUM existed in his world.
Lysandre has 3 cards in the TCG. The first one, entitled Lysandre, was first released in the XY: Flashfire expansion, and was later reprinted in XY: Ancient Origins. It lets you force one of you're opponent's benched Pokémon into play. Almost every deck used this card when it was in rotation. The second, entitled Lysandre's Trump Card was released in the XY: Phantom Forces expansion. It let you cycle all the cards in your discard pile back into your deck. This card was so good it had to be banned from play. The most recent card is Lysandre Prism Star, from SM: Forbidden Light. It lets you for each of your Fire Type Pokémon in play, put the same number of cards from your opponent’s discard pile into their Lost Zone. It hasn't been released yet, so it's too early to make a verdict on it's playability.