If held by a Delphox, the Delphoxite allows it to Mega Evolve into Mega Delphox if its Trainer has a Key Stone. A Trainer can only have one Mega-Evolved Pokémon at any given moment.
Reach Rank S in Ranked Battles Season 2 (November 6 - 26, 2025) Reach Rank V in Ranked Battles Season 3 (November 27 - December 17, 2025) Reach Rank W in Ranked Battles Season 4 (December 18, 2025 - January 7, 2026) Reach Rank X in Ranked Battles Season 5 or later (January 8, 2026 onwards)