Walkthrough
Just past Route 20 is Cinnabar Island, the location of the next Pokemon Gym. However, after arriving, you will quickly find that the Gym is locked and you must find the key to it in the Pokemon Mansion (also found on Cinnabar Island). Furthermore, there is another Research Lab found on this island, one that will revive any fossil you have into the Pokemon they once were.
Alolan Trade
Alolan Meowth: Trainers Requests Kantonian Meowth In Return
Obtainable Items
TM02: From Scientist In Research Lab
Antidote: Near Pokemon Mansion
TM46: Defeat Cinnabar City Gym Leader Blaine
PokeMart Items (Through Storyline Progression)
Poke Ball, Great Ball, Ultra Ball
Potion, Super Potion, Hyper Potion, Max Potion, Full Restore
Antidote, Burn Heal, Ice Heal, Awakening, Paralyze Heal, Full Heal, Revive
Escape Rope, Repel, Super Repel, Max Repel
Lure, Super Lure, Max Lure
X Attack, X Defense, X Sp. Atk, X Sp. Def, X Speed, X Accuracy, Dire Hit, Guard Spec.
Post Game
Walkthrough
After defeating the Elite Four and starting the Master Trainers Challenge, you will find a couple of Master Trainers on Cinnabar. In total, there will be two Master Trainers to defeat.
Trainers
Lass Cindy (Master Trainer): Level 75 Exeggutor
Hiker Lionel (Master Trainer): Level 75 Omastar