Walkthrough: After defeating all four members of the Elite Four, you will proceed to the Champion's Chamber. When you arrive, the room will be empty apart from a lone chair. As you sit on the chair as the Champion of the Alola League, Professor Kukui will appear and tell you that you have one more challenger to battle before becoming The Alola Region Champion. He will joke that this challenger is him, but unlike Pokemon Sun & Moon, he will step aside for the real challenger, Hau. After suffering loss after loss during his Island Challenge, Hau became determined to grow in his strength to defeat you in battle once and for all.
Pokemon Trainer Hau (Rowlet Starter): Level 59 Raichu, Level 58 Flareon, Level 58 Tauros, Level 58 Noivern, Level 59 Crabominable, Level 60 Primarina (Waterium Z)
Pokemon Trainer Hau (Litten Starter): Level 59 Raichu, Level 58 Vaporeon, Level 58 Tauros, Level 58 Noivern, Level 59 Crabominable, Level 60 Decidueye (Grassium Z)
Pokemon Trainer Hau (Popplio Starter): Level 59 Raichu, Level 58 Leafeon, Level 58 Tauros, Level 58 Noivern, Level 59 Crabominable, Level 60 Incineroar (Firium Z)