In Pokemon Legends: Z-A, the Ampharosite is a special Mega Stone that allows Ampharos to undergo Mega Evolution — temporarily transforming into Mega Ampharos with a significant boost in stats and a new ability. Acquiring this stone isn't as simple as finding it in the wild; it's earned through a challenging encounter that tests both your strategy and your readiness for late-game missions.

The Ampharosite is obtained after defeating a Rogue Mega Ampharos during Main Mission 23. Rogue Mega Pokemon are wild Pokemon that have managed to Mega Evolve without a Trainer's control. They are extremely powerful, capable of wiping unprepared teams in just a few turns.
Encounter Details:
When you defeat the Rogue Mega Ampharos, it will drop the Ampharosite as a reward. If you fail the mission, you can retry by revisiting the mission log or by speaking to the Team MZ handler in Lumiose HQ.
If you're looking to speed up your collection or want rare forms, you can always buy Shiny Pokemon Legends ZA from U4GM, a reliable platform trusted by players worldwide for fast and secure trading.
Once you've obtained the stone, equip it to your Ampharos via the Inventory → Held Items menu. During battle, a new Mega Power bar will appear beneath Ampharos's HP. When filled (typically by dealing or taking damage), you can trigger Mega Evolution, granting Ampharos a dramatic temporary transformation:
Mega Ampharos excels in both offensive and defensive roles, making it a solid pick for story progression and post-game challenges alike.
Among all the obtainable Mega Stones in Pokemon Legends: Z-A, Ampharosite stands out for its balance of power and accessibility. The battle against the Rogue Mega Ampharos is one of the game's best mid-late challenges — intense, cinematic, and rewarding. Once you've earned it, your team gains one of the most reliable special attackers in the region.