If held by a Baxcalibur, the Baxcalibrite allows it to Mega Evolve into Mega Baxcalibur 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 4 (December 18, 2025 - January 7, 2026) Reach Rank V in Ranked Battles Season 5 or later (January 8, 2026 onwards)
Trivia
In Pokémon Legends: Z-A, this item is able to be obtained by players who do not own the Mega DimensionDLC. Baxcalibur, however, requires owning the DLC to catch.