From Bulbapedia, the community-driven Pokémon encyclopedia.
Mirage Island (Japanese: まぼろしじま Phantom Island) is a hard-to-reach location in Hoenn.
In the games
Mirage Island is found on Route 130 in Pokémon Ruby, Sapphire, and Emerald. However, it can only be visited under highly rare circumstances. Every day, a random number between 0 and 65535 in hex (that is between 0x0000 and 0xFFFF) is generated by the game. If this number matches the last two bytes of the personality value of any of the Pokémon in the party in hex, Mirage Island will appear for that day. The number is generated at 0:00 hours every day and it is active for 24 hours. Even though play time has nothing to do with the real-time clock, a game that has reached the maximum time of play (999 hours and 59 minutes) will not generate Mirage Island numbers anymore.
Whenever a Mirage Island number is generated, it will not change within the time it is valid, and the player is able to freely move Pokémon from the boxes to the party or vice-versa until the Pokémon that has the same personality value as the island appears. This makes Mirage Island's appearance even rarer than encountering a Shiny Pokémon, although the probability of making it appear increases with the number of Pokémon the player has.
A man in Pacifidlog Town will tell the player whether or not he can see Mirage Island each and every day.
The island is inhabited by Wynaut which range from level 5 to level 50. It also bears a tree where one Liechi Berry can be picked. This is the best Berry for Pokéblocks, and will produce Gold Pokéblocks.
The same place without the island
| A colored background means that the Pokémon can be found in this location in the specified game. A white background with a colored letter means that the Pokémon cannot be found here.
In the anime
Mirage Island in the anime
In the episode Who, What, When, Where, Wynaut?, Ash and his friends landed on Mirage Island after Team Rocket's submarine exploded. May and Drew were stuck together and both end up nearly drowning when Drew passed out, before being saved by the Wynaut.
While the island does appear on maps, the whirlpools around it make it almost impossible to get to or from the island.
In the manga
In the Pokémon Adventures manga
Wally rescues the man searching for Mirage Island on Pacifidlog Island from being washed away from Kyogre's storm.
Ruby and Sapphire were washed up on Mirage Island, after meeting up with Juan, Tate and Liza, Juan explains that the time in the island is different from the external world and they were unconscious in the island for twenty-one days. The time on the island does not always travel at a constant speed and when the time on the island goes normal, one can get on or off the island, so Juan carries a Sandshrew-shaped hourglass for this reason. Ruby and Sapphire meet up with Plusle and Minun for the second time and use them to practice Double Battles with Tate and Liza, preparing for the final battle against Kyogre and Groudon.