Clarissa's Xerneas

 Clarissa's Xerneas   is a Pokémon she obtained in Kalos as a  Legendary Guardian.

Sparks: XYZ
Xerneas appeared in Sparks: XYZ when Clarissa was fighting against Team Flare. She aided the teenage Legendary Guardian and decided to join her in defeated Team Flare for good. Now on Clarissa's team Xerneas helped her up until she was turned to stone. Although she tried to revive her trainer with her Fairy Aura, she failed. Currently her whereabouts are unknown but it can be assumed she is trying to help Clarissa.

Trivia

 * Refered as a female