Mirage Island is an invisble Island located on Route 130. Most of the time it will be invisible but on rare cases, the island will be visible. To find out if the island is there or not, go to Pacifidlog Town and talk to the old man in the bottom right house looking out the window. He will tell you wheter the island is there or not. The cause is unknown so a bit of luck is needed to find it. On the island you will find the rare Leichi Berry that powers up your Pokemon's attack in battle when it gets weak. In the grass, you will only find Wild Wynauts.