Solsol seems to have a hatred of Team Flare. He didn't want to be captured by Y originally, but once he realized that she needed his help and Mega Evolution capabilities to stop Team Flare, he decided to join Y. Solsol is loyal to his trainer and becomes very powerful once he Mega Evolves.
Solsol was first encountered on Route 15. Y really wanted to catch him so she could own a Pokémon capable of Mega Evolution. He let himself to be caught willingly once Y explained that her goal was to defeat Team Flare. Shauna and Tierno went to find the Mega Stones for Solsol and Rute. A little while after they left, Essentia disguised herself as a nurse and stole Xerxer from Y and knocked her out. When Y became conscious again and met up with X and Essentia, Shauna and Tierno returned with the Mega Stones. Y was able to Mega Evolve Solsol, but felt agitated that her first opponent was Xerxer. Essentia commanded Xerxer to attack Y and Solsol, and they crashed into a wall. However, both were okay. X and his Mega Pinsir also helped fight the battle. After a tough battle, Essentia escaped and Xerxer returned to Y again. Solsol was praised and sent back into his Poké Ball.