S12E11 - White Thunder (1)
Synopsis
Having allowed it to gestate for a year, Elsa retrieves the White Dino Gem, with the intent of having it bond with Mesogog. But Trent, following the Invisiportal from his father's office, winds up accidentally, and painfully, bonded with the Gem instead.
He becomes the White DinoThunder Ranger, and pure evil, thanks to the genetic tampering done to the gem.