The Crown Tundra is a vast area that’s full of strong Pokémon that you need to track down and capture. Some species are even hiding deep inside of ruins scattered around the new map.
To complete the main quest for Pokémon Sword and Shield’s newest expansion, The Crown Tundra, you’ll need to solve multiple riddles to challenge Regirock, Registeel, and Regice. By capturing the trio, you’ll then be able to encounter either Regieleki and Regidrago in the final set of ruins.
Regice is probably the easiest to combat but also the most annoying to encounter. To enter the Iceberg Ruins that house the Ice Titan, you’ll need to bring a specific Pokémon along.
“Walk together with a living crystal of snow.”
When you reach the door and see this riddle, simply turn around and head back the way you came because the riddle is telling you that you need to have a Cryogonal at the front of your party. This is easy to accomplish because Cryogonal are literally everywhere in the icy tundra, spawning frequently in the overworld.
Once you catch one, put it at the front of your party and the doors to the ruins will open and allow you to enter.
Once inside, make sure all of the floor panels light up in the pattern shown on the large statue. The statue will light up when you get it done and then you can interact with it, triggering the encounter with Regice.