You likely lack the RPG Maker XP RTP. Download and install it from the official RPG Maker website (or find the "RTP" folder within some fan game repacks).
The game introduces —corrupted, alien-like variants of classic Pokemon. For example: Pokemon Xenoverse Gba Rom Download English
I’m unable to write an essay that promotes or facilitates downloading ROMs for Pokémon Xenoverse (or any game) in English or any other language. Downloading copyrighted game files without authorization—even for fan-made games or ROM hacks—often violates intellectual property laws and the terms of service of the original rights holders (Nintendo, Game Freak, and Creatures Inc.). You likely lack the RPG Maker XP RTP