From Bulbapedia, the community-driven Pokémon encyclopedia.
Lucario Kingdom (Japanese: ルカリオの王国 Lucario Kingdom) is an anime-exclusive location in Sinnoh. Riolu and Lucario have been revered as guardians for generations and are said to use their aura powers to protect the kingdom.
Prior to the events of Pokémon Ranger and the Kidnapped Riolu! (Part 1), a group of Pokémon poachers appeared in the Lucario Kingdom and stole the rare Aura Sphere Riolu from its Trainer. Riolu managed to escape two different groups of people interested in its power before the Pokémon Rangers stepped in to return Riolu to the Lucario Kingdom. Ash and his friends assisted Kellyn, and by the end of Pokémon Ranger and the Kidnapped Riolu! (Part 2), Riolu was reunited with its Trainer.
Pokémon seen in Lucario Kingdom