Anduu

Meet Aunduu, the corrupted Celebi.

When Dialga and Palkia went wild and space time distortions started forming all over, Anduu got caught up in one of the rifts formed and was pulled through. The overflow of power from the stronger legendaries infused itself within his body, and when he was finally able to get a grasp on what was happening, he found himself laying in a bed of flowers already looking like this. He tried to open a portal to return to the time he had been yanked from, only the usual green circle was instead a black and purple crack that showed the other time through it.

Anduu realized that he couldn't create normal portals anymore, and instead his powers would tear through the very fabric of space and time, to connect the two passages. Unable to safely travel the way that he was used to, he is now mostly stuck in the normal flow of time, taking care of different forests that he wanders between, often being mistaken as a bad omen by other pokemon and even humans. After all, a creature of nature and time turning black and being unable to hop around doesn't exactly bode well.