Yveltal appeared in Diancie and the Cocoon of Destruction as a being of destrucion where it destroyed the whole forest following the laws of nature. Later it went on deep slumber. When thieves following Diancie caused disturbance in the forest, Yveltal woke up and started to destroy the whole forest again in anger. Diancie tried to stop it but couldn't until Xerneas granted her energy to create large diamond. After that Yveltal went away flying peacefully.
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