Among the various places you can visit while Soaring, you will be able to find Mirage Spots. These spots are special areas in the sky or on islands inaccessible without flying, and only when you have achieved certain requirements, which will give you access to a variety of Legendary Pokémon. These Pokémon can only be obtained through these methods in this generation. Many of the Pokémon have certain requirements to unlock while some islands will appear randomly. - Serebii
A Mirage Spot is a random island that changes around everyday with different Pokemon at each one and sometimes even TMs and random items here and there. Certain Mirage Spots have legends at them. Here's a link: http://serebii.net/omegarubyalphasapphire/legendary.shtml That will give you everything about the legends you need to know. Hope this helps! -It's a secret!
