A Battle Royal is a Pokémon Rumble-esque type of battle in Pokémon Sun & Moon. It involves four Trainers battling each other at the same time. You can play on your own against three NPCs by visiting the Battle Royal Dome on Royal Avenue, or duel with up to three friends via the Festival Plaza.
Battle Royals are held at the Battle Royal Dome. The Battle Royal Dome has four corners: red, blue, green, and yellow.
Each corner has an entrance shaped like a Pokémon's head: the red corner is shaped like Charizard, the blue corner is shaped like Gyarados, the green corner is shaped like Tyranitar, and the yellow corner is shaped like Haxorus.
In a Battle Royal, each player brings three Pokémon, using one Pokémon at a time. At the end of a turn, if a player has no Pokémon left, the Battle Royal ends.
If a Trainer's Pokémon knocks out an opposing Pokémon, that Trainer receives a point. If a Pokémon faints due to indirect damage, such as poison or burn, the point is awarded to the Pokémon who caused the indirect damage to occur. If a Pokémon faints due to self-inflicted damage or effects, such as from recoil or Explosion, no points will be rewarded to anyone.
The battle is over at the end of the turn after all of any one Trainer's Pokémon have fainted. The winner is determined based on the combined total of the KO points they earned and their remaining conscious Pokémon.
If there is a tie, the winner will be determined based on whose Pokémon have the most remaining HP. A Trainer who had all of their Pokémon faint cannot win, even if they have the most points, unless all three opponents also lost all of their Pokémon.
While the rules are basic, the players must carefully consider who to attack and who to save – if so inclined. The unpredictability of it brings something fresh and new to the table. Trying to anticipate what your opponensts will do next and forge battle strategies is half of the fun.
When playing against NPCs, there are four ranks you can battle in:
You unlock each rank by winning a battle in the previous rank. By beating the Master Rank, you get the Battle Royal Master Ribbon and you unlock the Idol Battle Style.
You get Battle Points (BP for short) for each Single Player Battle Royal you participate in. You gain 1 BP if you lose the battle, 2 to 4 if you get second/third place, and 2 to 5 BP if you win. The amount of BP you gain for winning or getting second/third place depends on the rank you're playing in.
You can use BP to buy items in the Battle Royal Dome or at the Battle Tree.