Mirage Island in Pokémon Emerald is one of the rarest and most mysterious locations in the game. Hidden off the coast of Pacifidlog Town, this small island can only be seen under very specific conditions. Its appearance is entirely determined by an invisible number system running behind the scenes, making it one of the hardest events to encounter naturally in the Hoenn region.

How Mirage Island Works
Each day, the game generates a random number called the Mirage Island value, which ranges from 0 to 65,535. Every Pokémon in your party also has a hidden Personality Value (a unique 32-bit number that influences things like nature, gender, and even shininess). Mirage Island will appear if — and only if — the last two bytes of any Pokémon’s Personality Value match the day’s Mirage Island value.

In simpler terms, it means that one of your Pokémon’s secret identification numbers must align perfectly with the daily hidden number generated by the game. If no Pokémon in your party matches the day’s number, Mirage Island remains invisible.

How to Check for Mirage Island
There is one way to find out if the island is present on that day. Visit the elderly man in Pacifidlog Town who lives in the house on the southeast side of town. Each day, he checks your current party. If one of your Pokémon’s hidden numbers matches the day’s Mirage Island value, he will tell you he can see the island. If not, he will simply say he cannot.

What Happens When It Appears
If the conditions are met, Mirage Island becomes visible to the east of Pacifidlog Town. You can then surf to it and explore. The island features the following:

• Wild Wynaut (Level 5–50), which are exclusive to this location.
• Liechi Berries, the rarest berry in the game, growing in a patch on the island.
  Once Mirage Island is visible, it remains available for that entire day but disappears the next day unless the random number matches again.

Odds of Seeing It
The probability of Mirage Island appearing is extremely low — roughly 1 in 65,536 per Pokémon in your party. With six Pokémon, that gives you about a 1 in 10,923 chance each day. Because of this, most players never encounter Mirage Island naturally without external tools or luck.

In Summary
Mirage Island in Pokémon Emerald appears only when one of your Pokémon’s hidden Personality Values matches the game’s randomly chosen daily number. You can check its presence by talking to the old man in Pacifidlog Town. If it appears, it offers a rare chance to catch Wynaut and collect Liechi Berries. Its rarity makes it one of the most legendary secrets in the Hoenn region — a reminder that some of Pokémon’s most fascinating mysteries lie hidden in pure chance.