A colored background means that the Pokémon can be found in this location in the specified game. A white background with a colored letter means that the Pokémon cannot be found here.
Treasure Hunter's House
The Treasure Hunter's house stands on a small island to the southeast. He loves to collect Shards, and is happy to trade for them with certain evolutionary stones. The kind of Shard you trade him determines the kind of stone you get in return.
Mossdeep City stands perched on an island near Hoenn's eastern edge, where the winds are mild and the weather conditions are stable. This makes it the perfect place for launching rockets, and a perfect home for the Mossdeep Space Center. The seventh Gym in the Hoenn League, run by twin Gym Leaders, is located on the north side of the island, and Steven's house can be found on the island's northwest corner.
The first person you meet upon arriving in Mossdeep is a Black Belt in the shallow water on the island's southwest side. As a Fighting-type Trainer, he's had a difficult time at the local Gym and has resorted to punching the ground to relieve his frustration. Speak to him, and he offers to teach the move DynamicPunch to a Pokémon, one time only.
The house on the island's northwest edge belongs to Steven, and contains part of his rock collection.
Visit the house nearest the stairway to the Space Center to meet a young woman who uses a Wingull to send letters to a friend in Fortree City. Talk to the Wingull and it will take flight, off to deliver another note. If you return to Fortree and visit the Pokémon Breeder in the northeast house there, he will give you a Mental Herb that his Wingull found in its travels.
Score the Super Rod
The house overlooking the Gym belongs to a lone Fisherman. Speak to him to receive the Super Rod, a high-end fishing rod that can reel in all kinds of sea life.
Mossdeep Space Center
The Mossdeep Space Center stands on a hill in the northeast. Steven is inside, standing near a table with a letter emblazoned with the Team Magma logo. It seems that the group has announced its intention of stealing all the rocket fuel on the island. He plans to keep an eye on things for now, and suggests checking out the rest of the city. A Sailor near the viewing area will give you a Sun Stone he found on the beach.
Mossdeep City Pokémon Gym Leaders: Liza & Tate
The mystic combination!
The Mossdeep Gym specializes in Psychic-type Pokémon, which are vulnerable to Dark- and Ghost-type moves. Dark Pokémon are both immune to Psychic moves and able to inflict super-effective damage. Three of the gym leaders' Pokémon have additional weaknesses to Water and Grass. While they're also weak to Bug, Bug attacks are generally too weak to be worthwhile. The Gym features several rooms linked only by warp tiles. Each room contains Trainers and obstacles on spin tiles that rotate when certain tiles are stepped on, changing the path and often bringing challengers within view of opposing Gym Trainers.
Step on the warp tile on the west side of the first room. Begin a battle with Hex Maniac Kathleen and Gentleman Clifford. Go west and step on the purple tile, and then battle Psychic Macey. Continue south and step on the green tile twice; this spins the obstacles in the south-central room. Take the north warp to the west-central room, then the left warp there to the northwest room. Step on the first blue tile twice, battle Gentleman Nate and Psychic Virgil, step on the orange tile three times, battle Hex Maniac Sylvia and Psychic Hannah, step on the second blue tile three times, and step on the first blue tile once to reach the warp tile. Cross the south-central room to the last warp and the Gym Leaders' room.
Twins Tate and Liza send out two Pokémon at once, drawing challengers into a Double Battle. Claydol can boost its already-high Special Defense with Light Screen, and simultaneously hit two of your Pokémon with Earthquake. Xatu's Calm Mind raises both its Special stats, and Confuse Ray allows it to harass the foe. Lunatone can lull its opponent to sleep with Hypnosis, while Solrock can scorch Grass Pokémon looking to target their Rock typing. Three of their Pokémon are weakened by Water moves; by using Surf, you can attack both at once and bring the battle to a quick end. Otherwise, you may want to target one Pokémon at a time in what would essentially become a two-on-one battle.
After beating the Gym, you find Maxie and several Grunts on their way to the Space Center. Follow them inside and defeat the four Grunts on the first floor. Upstairs, you are ambushed by three more; you fight them one at a time, but with no break between. Farther on, you find Steven confronting Maxie, who reveals his intentions for the rocket fuel. With Groudon gone, he has no need for their base. They're going to cause Mt. Chimney to erupt by dumping the entire supply into the volcano! Steven is shocked, and asks you to join him in battle against Maxie and Tabitha. Steven's team consists of Metang, Skarmory, and Aggron.
Having failed at both controlling Groudon and activating the volcano, Maxie begins to questions his goals and wonders if Team Aqua's plans are equally misguided. Maxie and his subordinates flee, and Steven invites you to his home. He greets you when you step inside, and hands you HM08 (Dive). In certain bodies of water, there are dark spots where the water runs unusually deep; using Dive at one of these spots lets you descend to the ocean floor far below. Swim to a point where the sunlight filters down from above and use Dive again to surface. With this move, you will be able to pursue Archie to the Seafloor Cavern.
Route 125 (optional)
Located north of Mossdeep City, Route 125 is an optional area with several potential Secret Base locations. The waterlogged Shoal Cave stands in the route's center.