Mighty Challengers Stand before You in Legacy Trainer Showdown
In the Legacy Trainer Showdown event running from September 9, 2022, to October 6, 2022, when a Unite Battle begins, Leon, Raihan, Cynthia, Korrina, and Green will randomly burst in to face off against you. Try your hand at defeating them!
In order to challenge these Trainers, you’ll need to use Trainer battle tickets. During the event, you can receive one Trainer battle ticket per day at no cost and exchange Aeos coins for additional tickets. You can also earn Trainer battle coins based on your performance and exchange them for items, such as Trainer Outfit (Leon). Don the fashion of the unbeatable Galar champion!
Source: Official Pokémon UNITE website