In "The Arceus Chronicles," Heatran serves as a pivotal figure. This Legendary Fire/Steel-type Pokémon falls under Team Galactic's control, commanded by Saturn. Captured to reactivate a dimensional gateway and retrieve their former leader Cyrus, Heatran is forced to channel energy through the Flame Plate—an artifact intrinsically linked to Arceus. An energy overload triggers a malfunction in Heatran's innate Flash Fire ability, plunging it into a violent, uncontrolled berserk state. This overload engulfs Heatran in intense flames and induces physical mutation, revealing molten lava beneath its usual metallic shell.

Heatran's physiology features a body of rugged steel, partially melted by its own immense heat. Boiling, magma-like blood circulates internally, contributing to its intense thermal presence. Cross-shaped claws enable it to traverse volcanic caves, ceilings, and walls. It remains the sole Pokémon capable of wielding its signature volcanic move, Magma Storm.

In its berserk state, Heatran rampages across Sinnoh, targeting Mount Coronet's Spear Pillar—a site tied to Team Galactic's past schemes. The uncontrolled flames and destruction draw intervention from Ash, Goh, Dawn, Brock, and later Sinnoh Champion Cynthia. Initial attempts to calm or subdue it fail against the overwhelming heat radiating from its mutated form. Direct intervention by the Lake Guardians—Azelf, Uxie, and Mesprit—using psychic means, combined with Arceus's indirect influence through the Flame Plate, ultimately quells Heatran's rampage and restores its original state.

Broader lore frames Heatran as an embodiment of the planet's core, birthed from magma within volcanic mountains like Mount Coronet. Artifacts such as the Magma Stone traditionally control or seal it, preventing eruptions. Without these safeguards, Heatran's power can destabilize its environment, aligning with its destructive portrayal under Team Galactic's misuse.