Hoenn has always had an incredible amount of Water Pokemon in the area, which is why when people heard of a new odd gym that was on and off, it was immediately thought to be a new Water Gym.
You, as a challenger, prepare yourself with the mightiest of grass-types and electric-types, including your good old Scizor, because you are sure that Rain will weaken any sort of Fire moves they would somehow throw at you.
Heading towards Pacifidlog, you ask an old man whether the gym has appeared. To your surprise, it has! You quickly hop on your Surfing Pokemon and head towards the odd island that is Mirage Island.
The many Wynaut surprise you. You thought they were extremely rare! As you try to approach one to capture, a Flareon jumps out of the grass and growls at you! You're not well prepared for Fire Types, but the Gym is surely a Water-type one! "Calm down, Jet. I am sure this is a challenger." An old man's voice calls out to the named Flareon. He stops growling and stretches out. Phew! Wait, challenger?
An orange-haired man approaches you. It must be the Flareon's owner. "I assume you have come to take on the Gym Challenge?" You nod. "Then, by all means, I am someone you can train with. Michael Helix, of the Mirage Island Gym! The fiery spirit upon me and my fire types will scorch you, but not this land!" Fire types?! Oh no, this isn't good! The Wynaut surround you and the leader, trapping you from leaving. Michael sends out his Pokemon.... humans?! And the Flareon too! You send out your Pokemon, and find out they're humans as well! Ugh, you think the sun may be doing a bit too much to your head...
Summary:
Permanent changable Sun.
Burn is stronger due to the sun. Burn's physical attack BAP reduction is 4 instead of 3. In addition, all moves with a burn chance have that chance doubled and Will-O-Wisp has 100% accuracy. Hah! You better have Burn Heal!
Due to the fact that Mirage Island counterbalances the power of spread moves by tilting ever so slightly, and that it is in the air, all spread moves' BAP are reduced to 50% their original BAP. This includes, but is not limited to; Earthquake, Surf, and Lava Plume.
The tilting will also affect hazards. All hazards have 50% effect. (Stealth Rock and Spikes deal 50% damage; Toxic Spikes will only Poison regardless of number of layers; Sticky Web is negated entirely.)
Camouflage turns the user into a Fire-type; Nature Power becomes Fire Blast and Secret Power has a 30% chance to burn.