Pokemon Diamond, Pearl, Platinum, Brilliant Diamond, Shining Pearl

When the player first arrives in Canalave City, they are told to train at Iron Island before challenging the Canalave Gym. It's an island to the North where lots of rock and steel Pokemon reside. A ferry in the city will take you there. Once the player has explored Iron Island fully and fought off Team Galactic, the Canalave Gym opens for business, with Byron the Steel expert as its Gym Leader.

Byron's gym design is fun: the gym is very tall, with multiple floors that you have to go between by standing on these elevators. Some will only move you one floor up or down, while the red ones move you multiple floors.

Byron talks some crap about his son Roark, the Oreburgh City Gym Leader you fought first on your journey. Apparently it's embarrassing to lose to a rookie trainer, according to Byron. Let's give him a taste of what it's like!

Byron uses three Pokemon in his gym team. Kind of underwhelming for the sixth gym leader...

He leads with a Pokemon you will have gotten so tired of by now in Bronzor. It's a Steel/Psychic type native to Sinnoh, and its gimmick is making you guess what ability it has. 50% of the time they will have Heatproof, lowering your fire damage by a lot, while the other 50% it will have Levitate, making your ground moves ineffective. It's really good at shutting down one of its two weaknesses that way. This particular Bronzor has Levitate. Byron's next Pokemon is a Steelix. It can hit quite hard but goes down fast to special hits. In Platinum, Bronzor is replaced by a Magneton.

Byron's last Pokemon is one of the fossil Pokemon of the Sinnoh region, Bastiodon. It's the counterpart to Rampardos, who thematically is his son's Roark's signature Pokemon (or at least its evolution). Bastiodon is a very interesting Pokemon to face, as it is purely defensive. It has very little to no offensive damage output, and relies on countering all damage you do to it with its move Metal Burst. It can also use Rest to heal itself and Iron Defense to boost its defense stat a lot.

Defeating Byron will grant you the Mine Badge. He will act excited at all the new upcoming trainers and vows to train hard to beat them. At least he's a decent sport.

In Platinum, Byron can be found on Iron Island during the post-game. He will talk to you a bit about how he's been treating his son Roark, and the regrets he has about it. It's honestly quite nice to see this growth, I wish we could see him have this interaction with Roark himself.

Also in Platinum, Byron will be available for a rematch in the Battle Zone, a small island offshore of the mainland of Sinnoh. In the post-game, you can challenge Byron to a battle. He will use his fully evolved gym team, including the newly introduced Magnezone, evolution of Magneton. He also adds a Skarmory and an Aggron to his team.

In Brilliant Diamond and Shining Pearl, Byron can be rematched in his Gym instead. He uses the same team as the Platinum rematch, but adds an Empoleon to his party! He is also an opponent in the Battle Tower, even appearing alongside Roark in the Double Battle Challenge.

Pokemon Black 2, White 2

Byron returns alongside his fellow Sinnoh gym leaders for the Pokemon World Tournament. He can be fought in the Sinnoh Leaders and Type Experts challenges. He uses mostly the same Pokemon as his gym teams, adding a few extras like Forretress and the new Excadrill.

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Byron is a gym leader I wish we saw a bit more of. He's one of the more quiet/irrelevant gym leaders of the Sinnoh Region when it comes to the story, and it's a shame because his connection to Roark is interesting.

He's clearly this big imposing figure, and a strict dad to Roark. He values strength and almost looks down on his son for losing to inexperienced trainers, despite that being Roark's position as the first gym leader of the region. If this was all we saw of Byron, I would dislike his character a lot. I do appreciate that they gave him a moment to self reflect in Platinum, and that we see him realize that he should treat Roark with more respect. In the anime this was a big part of his story, so I'm glad they included it in the game as well.

I doubt we will ever see him again in some cameo as he's neither relevant nor popular.