The extra rare Keldeo is available for all to download if you have Pokémon X & Y and Omega Ruby & Alpha Sapphire. Keldeo has been a particularly difficult legendary Pokémon to obtain, similarly to Genesect and Meloetta. In fact, I only remember one local distribution event, and that was at rAge a number of years ago.
If you’re looking to get your free Keldeo, all you have to do is retrieve him from the Mystery Gift menu. Simply enter mystery gift from the main menu, select receive gift from the internet and you should have a nice new legendary on your team. He will know the moves Leer, Double Kick, Aqua Jet and Bubble Beam. You can get one Keldeo for each copy of Pokémon you have, so make sure you get the maximum.
We’ll keep you posted with next month’s free Pokémon, which I believe is Genesect and then Meloetta.