Just outside the town exit of Freezington, you will find a small tree with Footprints under it. As you approach these footprints, Sonia will suddenly appear. After getting reacquainted, she will tell of her theory about three Legendary Pokemon having a secondary home on the Crown Tundra. She will ask that you search the Crown Tundra for the footprints of these three Pokemon, asking for you to return to her in Freezington after you have found all of the footprints for each. There are a total of fifty footprints for each of three Legendary Pokemon in question, which includes the Iron Will Pokemon, Cavern Pokemon and Grassland Pokemon.
The Cavern Pokemon is none other than Terrakion, one of three Pokemon apart of the Legendary Swords of Justice Trio from the Unova Region. In order to find all fifty of the Terrakion Footprints, you will need to extensively search Lakeside Cave, Ballimere Lake and their given nearby areas. Luckily, most of them should continue down certain paths, making it not all that difficult to find all fifty of them. After finding all fifty of Terrakion's Footprints, return to Sonia in Freezington to update her. With this new bit of information, Sonia will tell you that you should be able to find Terrakion in Lakeside Cave.
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