Magby made his debut in A Cast-Iron Heart!, where he worked in the Fuego Ironworks alongside several other Fire-types. One day, while Mr. Fuego was away, the controls malfunctioned, shutting off the machinery and locking down the Ironworks, preventing anyone from getting in or out. Due to this, the Fire-types were forced to remain in the Ironworks and attempt to fix the machinery themselves.
The group, alongside Mr. Fuego, managed to gain entry into the Ironworks thanks to Nate's Magnezone and met up with Magby and the other Fire-types. While Nate and Bianca helped Mr. Fuego fix the controls, Lewis and Magby began to relight the forges. With Lewis' encouragement, Magby managed to learn Flamethrower, using it to light the forges and restore the Ironworks to working status.
As the group prepared to continue on to Hearthome City, Magby approached Lewis and challenged him to a battle. Lewis happily accepted and battled Magby with Piplup. Despite having a disadvantage, Magby was able to hold his own, but was eventually damaged by Bubble Beam. Lewis then threw a Poké Ball and caught the Live Coal Pokémon.
Magby was Lewis' first Pokémon in his Gym battle against Fantina in Relics of the Past! It faced off against Fantina's Duskull, who used Calm Mind to boost its Special Attack and Special Defence. Magby was able to defeat Duskull with Flamethrower after using Clear Smog to reset its stats. He then battled against Drifblim, but was defeated by Gyro Ball.
Magby is shown to be a very passionate Pokémon and possesses a strong heart. His desire to restore the Fuego Ironworks was strong enough to rally the other Fire-types into helping. Despite this, Magby occassionally suffers from a lack of confidence, although is able to be cheered up by Lewis. Due to this, Magby forged a strong connection with the Trainer and always seeks to do his best in battle.