Keldeo is one of the legendary Pokémon you can capture in Pokémon Sword and Shield’s Crown Tundra expansion. The new region features a variety of Pokémon from the mainline series, and you can expect to see new twists on old favorites, such as Galarian versions of Articuno, Moltres, and Zapdos. Keldeo does not have a new form, but you can catch it and use it in the Galar region. Unfortunately, it is also shiny locked, so there is no shiny form you can catch.
Keldeo only arrives after you’ve captured the three Swords of Justice Pokémon, Cobalion, Virizion, and Terrakion. These Pokémon appear after you discover a set of their footprints outside of Freezington. You meet up with Sonia, who helps you track them down throughout the region. There are 50 Pokémon tracks for each of these legendary Pokémon, so you can expect to thoroughly explore Crown Tundra to find them all.
Once you have them all, and you’ve captured the legendary Swords of Justice, Keldeo is now ready for you to capture. You need to have Cobalion, Virizion, and Terrakion in your party before venturing out, so make sure that they’re sitting in your roster. With them, head to the southern portion of Crown Tundra, specifically to the Ballimere Lake. When you arrive at the lake region, look for a small island that has a pot off to the left side of it, behind a tree. The island is to the southwest of the Dyna Tree Hill marker.
You can set up camp with your Pokémon at this location and make up a batch of curry. You can make any variety of curry you want to cook, so don’t worry about the ingredients too much. After you make and eat the curry, exit the camp and Keldeo will be wandering around the area nearby. Run up and do battle with it to capture it, and add Keldeo to your collection.