Side Mission 106 in Pokemon Legends: Z-A(Klefki's Lost Key) cannot be started until after you reach Rank A in the Z-A Royale, but it'll involve you having to find a lost key for a Pokemon trainer ...

Like other keys in Warzone Season 4, there’s more than one way to ascertain the Lost Room 403 Key. We’ll run through each below, explaining the best methods to find it and then where to take it to use ...