The easiest way to find Keldeo is in Sword and Shield's Crown Tundra DLC, where it can be battled at Ballimere Lake after Cobalion, Terrakion, and Virizion have been captured. This is the only way to obtain Keldeo that doesn't require the use of limited events.
Keldeo is obtainable through the DNS Exploit in Black 2 and White 2, which uses fan-hosted servers to access old Mystery Gifts. For help with setting up the exploit, reference our detailed guide. A Keldeo obtained through this method is legitimate and will pass hack checks.
