S12E25 - Tutenhawken's Curse
Synopsis
Ethan takes an interest in deciphering the hieroglyphics of Egyptian ruler Tutenhawken. In doing so, he not only jinxes himself, causing chaos at his every step, but frees the ancient evil from his multi-millenna-long slumber. Mesogog ceases from intervening, sending Elsa out to help the third-party-evil only at the last minute. Hayley's newest invention, the Hovercraft Cycle, is just what Ethan needs to make Tutenhawken history again, in his own territory of the air, and the Triassic Mega-Rover finishes the job.
During his brief re-reign, Tutenhawken took an interest in Cassidy (or Cassipatra as she called herself), which conflicted with the progress she and Ethan had been making in showing people her better side. The monster's treatment of Devin, though, led her to resume the right track, and bridges are mended between her and Ethan.