Z-moves, regional variants and the end of gym battles.
Sun, Moon, Ultra Sun, Ultra Moon · Released 2016
Alola is the Gen 7 region, and the generation that made the biggest structural change to the Pokémon formula since Gen 1: it removed gyms entirely. Instead of 8 gym leaders, Alola uses a 'trial' system where players complete themed challenges on each of the four islands, culminating in a Totem Pokémon boss fight. Gen 7 also introduced regional variants (Alolan Raichu, Alolan Muk, etc. — Pokémon with alternate typings based on their new habitat) and Z-moves (one-use super attacks per battle).
Alola is based on Hawaii — four islands (Melemele, Akala, Ula'ula, Poni) directly corresponding to Oahu, Maui, Hawaii Big Island and Kauai. Hawaiian language is woven throughout (kahuna, mahalo, mauka/makai). Solgaleo and Lunala reference the sun and moon of Hawaiian mythology, and the Ultra Beasts are pulled from a sci-fi subplot about parallel universes.
Sun & Moon shipped at the exact 20-year anniversary of Pokémon Red & Blue, and the in-game Battle Tree features Red and Blue (now adult trainers) as endgame bosses — the first time the original protagonists are explicitly playable opponents in a mainline Pokémon game.
Sun and Moon introduced regional variants: existing Pokémon reimagined with different typings, stats and sometimes evolutions to reflect a different environment. Alolan Vulpix is Ice rather than Fire, Alolan Marowak is Fire and Ghost, Alolan Raichu gains Psychic. It has since become a fixture of every generation.
Alola also removed HMs, replacing field moves with Ride Pokémon and freeing up move slots that had been wasted on Cut and Surf for two decades. Z-Moves, once-per-battle attacks unlocked by a crystal, arrived and departed in a single generation.
The traditional gym structure was replaced with island trials and Totem Pokémon — a change that has not returned, but which produced some of the more memorable set-piece battles in the series.
Alola introduced the Ultra Beasts, a group of extradimensional Pokémon with deliberately lopsided stat spreads — Pheromosa's enormous Speed and Attack against paper defences is the clearest example. Several were strong enough to require their own tiering decisions.
Toxapex deserves a mention as one of the most durable defensive Pokémon ever released, and Mimikyu's Disguise ability, which absorbs one attack entirely, made it a fixture of competitive play for years.
Regional variants of existing Pokémon with different typings, stats and sometimes different evolutions, reflecting adaptation to Alola's environment. Alolan Vulpix is Ice instead of Fire and Alolan Marowak is Fire and Ghost. They are permanent species differences, not temporary transformations.
A group of extradimensional Pokémon introduced in Sun and Moon, characterised by extreme and deliberately unbalanced stat spreads. Pheromosa pairs enormous Speed and Attack with almost no bulk, and several Ultra Beasts required their own competitive tiering decisions.
88 new Pokémon, numbered #722 Rowlet through #809 Melmetal, plus 18 Alolan variants of existing species which are catalogued separately because their typings and stats genuinely differ.