You can watch this and other Battle Frontier episodes on platforms like Prime Video or the official Pokémon TV channel . If you're looking for more info, Abra and the Psychic Showdown | POKÉMON FULL EPISODE 21

The group falls into an underground ruin where Ash, ignoring warnings, touches a stone sphere and is possessed by an ancient king.

In this pivotal episode, Ash and his friends discover the Battle Pyramid while traveling through the Kanto region. After accidentally falling into ancient ruins, Ash becomes possessed by the spirit of the evil King of Pokélantis. Key Plot Points

Brandon, the Frontier Brain of the Battle Pyramid, challenges the possessed Ash to a battle. Brandon uses his Regirock against Ash's Sceptile .