* "Mirage Island" in Pokémon Diamond & Pearl: This is a location in the Sinnoh region that can only be accessed through a specific event.
* The Pokémon you can catch there are Manaphy (through an event) and Phione (by breeding a Manaphy).
* "Mirage Tower" in Pokémon Omega Ruby and Alpha Sapphire: This location can only be reached by finding a hidden island that appears in certain weather conditions.
* The Pokémon found there are Latias and Latios.
* "Faraway Island" in Pokémon Black and White: This location is accessible through a specific event.
* The Pokémon found there are Keldeo, Meloetta, and Genesect.
Let me know if you were thinking of one of these locations or if you can provide more information about the "Mirage Island" you're thinking of!