Arena idea!
The De-Generator
Similar to the Elements of Change arena, you and your pokémon are suspended on a platform high into the air. Unlike Elements, however, your pokémon's types don't change every round. Instead, your pokémon are locked out of their traditional abilities and are linked to the abilities of the arena. Every three rounds, a RNG will issue an different ability for the arena that both pokémon are subject to. This ability can be any of the abilities released so far, even abilities exclusive to legendary and banned pokémon.