Steven Stone is the Champion of Hoenn's Elite Four in Pokemon Ruby and Sapphire, though he steps back to a wandering trainer role in Emerald after passing the title to Wallace. He's known as a Steel-type master, with Metagross as the foundation of his team.
He's the son of the Devon Corporation president and shares his father's passion for collecting rare stones. Steven lives in Mossdeep City, and when you beat the Elite Four, he'll leave behind a Beldum and a note as a parting gift.
In the anime, Steven made a brief appearance in "A Hole Lotta Trouble," helping Ash and friends escape from an underground cavern alongside Team Rocket. The encounter left such an impression that Ash vowed to train hard enough to battle him someday.
In Pokemon Adventures, things get more complicated. Steven meets Ruby while exploring Granite Cave and actually helps trigger Skitty's evolution when it bumps into one of his Moon Stones during a wild Mawile fight. He knows about the threats posed by Team Magma and Aqua and tries recruiting Ruby to help—but Ruby declines because he's not really into battling at that point. Steven's fancy arm devices let him chip away at stone and retrieve rocks from hard-to-reach places.
It turns out Steven and his father have known about the villainous teams' plans for ages. Mr. Stone even built the Submarine Explorer 1 specifically so Steven could seal off the Seafloor Cavern and prevent anyone from awakening Kyogre and Groudon. As backup, they'd unseal the legendary Regis if needed.
When things escalate, Steven rallies the rest of the Elite Four for a final stand. With Sapphire's help—her Wailord and Relicanth are key to opening the Regis' chamber—they manage to unseal Regirock, Regice, and Registeel. Steven bonds with Registeel while the others take the remaining two.
Here's the heavy part: knowing he'll die from the strain, Steven voluntarily steps down as Champion and returns the title to Wallace, revealing that Wallace was actually the real Champion all along and Steven had just been filling in. Steven seemingly doesn't survive the ordeal of controlling Registeel, but mysteriously gets revived later when Ruby releases his Celebi.
After that, Steven drifts to Sinnoh to hunt for rare stones in the region. He even buys a villa there before eventually selling it to Platinum and heading back to Hoenn.
When he needs to get around, Steven rides his Metagross—the magnetic field it produces lets him float right on top of it.
Content compiled by AnimeList.moe from publicly available sources.
