You can get a King’s Rock from a wild Slowpoke holding it. Catch some Slowpoke in Sevii Island’s Sevault Canyon to check if it’s holding King’s Rock. Since Slowpoke is only available in the LeafGreen version, you can get a King’s Rock in the FireRed games by beating a challenge in Trainer Tower.
Sevault Canyon Entrance
As mentioned, Slowpoke can only be found in the wild in the LeafGreen version of the games.
To catch some Slowpoke, head to Seven Island using your Rainbow Pass. Slowpoke can be found in Sevault Canyon.
From the island Poké Center, cross the bridge to the south until you reach the Canyon Entrance.
Follow the path until you get into some tall grass. You can start your search here and extend throughout the Sevault Canyon.
Slowpoke has a 10% chance of appearing in the tall grass around the canyon, and there’s a 5% chance that the Slowpoke is holding a King’s Rock. It’s recommended to have empty slots in your party so that you can check if the Slowpoke you’ve caught is holding a King’s Rock or not. You might need to catch a number of Slowpoke until you find one that’s holding a King’s Rock.
Alternatively, you can also have your Pokémon steal from Slowpoke instead of catching a ton of them. The move Thief and Covet can deal damage and can steal the foe’s held item. Take note though that only Snorlax can learn the move Covet.
Trainer Tower
Since Slowpoke cannot be found in the FireRed version of the games, the alternative of getting a King’s Rock aside from trading is to win one as a prize in Trainer Tower.
Trainer Tower is also located on Seven Island. From the Pokémon Center, head north until you reach a shore. Have your Pokémon use Surf on the body of water to cross to the other side.
The Trainer Tower should be on the other side.
Enter the tower and stock up on items for battle such as healing potions and revives. Once you’re ready, talk to the receptionist to take on the Mixed Challenge.
The goal is to make it to the top of Trainer Tower by battling eight floors of trainers either in a one-on-one match or doubles. If it’s your first go, there’s a time record to beat to win the prize. It should be doable to beat the record even if the battles are challenging.
When you reach the floor, the trainers you battle will have the same level as the strongest Pokémon in your party. It might prove to be a challenge, so you can Save and Restart should you lose, but once you do succeed, you get the King’s Rock prize.
Take note that unlike in the LeafGreen version, this method of getting the King’s Rock is not repeatable.
Using the King’s Rock
The King’s Rock is intended to be a held item by Pokémon. When held, it gives moves a 10% chance of causing the foe to flinch.
When held by Slowpoke and Poliwhirl, they can evolve upon trading into Slowking and Politoed respectively.
