This event is available after you enter Frostpoint Field from the exit that’s near the Freezington base camp. If you’ve completed the main story, you’ll be directed to some footprints by a tree. Afterwards, Sonia will show up and ask you to find as many footprints as possible.
The footprints belonging to the Cavern Pokémon, Terrakion, are large, circular and dark in colour. They’re generally quite easy to spot, although they can camouflage in places with muddy terrain. It’s also easy to mistake them for rocks or pebbles. If in doubt, go and take a closer look–nobody will think you’re dumb for staring at pebbles.
From our observations, Terrakion’s footprints start from the southern edge of the Giant’s Bed, right near the river that leads to Ballimere Lake. They’re most commonly found in Ballimere Lake and inside the Lakeside Cave. The cave has the most dense distribution, but it’s small, so you’ll need to search the lake as well.
Pokémon Sword & Shield: The Crown Tundra - Ballimere Lake Footprints
We show you where to find 50 of the Cavern Pokémon, Terrakion's footprints in Ballimere Lake.
Once you’ve found 50 footprints and achieved 100% completion rate, report your results to Sonia back at Freezington. She’s in the middle house. Surprise, surprise, the Cavern Pokémon has made the Lakeside Cave its home. You’ll find the brutish beast roaming around the deepest part of the cave, which isn’t all that deep.
This bullish Legendary boasts excellent Attack and otherwise solid stats, besides its Sp. Attack, which it doesn’t need. Although it might look slow, it has above average Speed. So be wary if you’re using slower ’mons. It has the same attacks as Cobalion, but swapping Iron Head with Stone Edge.
Like Cobalion, going in without a plan (or overpowered Pokémon) is a recipe for disaster. Terrakion has high Attack already, but after a few uses of Sword Dance, it can easily one-shot Pokémon of a similar Level. A Ghost-type is ideal to nullify its Fighting-type moves. If it’s also Ground or Steel (like Runerigus or Aegislash), even better.
Otherwise, follow the same plan with every other Legendary or hard-to-catch Pokémon. Start by inflicting paralysis, unless you have other ideas. Then slowly but surely weaken Terrakion down. Avoid Dark-type moves, as they will trigger Justified. If you KO Terrakion, pop into Pokémon Camp for a moment to respawn it.
When you’re content with Terrakion’s HP bar and there’s a suitable Pokémon ready to receive Terrakion’s punishment, go ahead and unleash your best Poké Balls. Since you’re inside a cave, you don’t have to worry about the weather getting in the way. You can also use Dusk Balls regardless of the time of day. Easy, peasy! (But it can still take ages.)