And summoning the Grimm Troupe, but that’s a much longer quest.
Crystal Peak is one of those locations that’s probably important lore-wise but very much not explained. The crystals seem to contain the light of the kingdom’s adversary, the reason for the seal, according to the Dream Tree. That’s why there’s that huge monument at the top of Crystal Peak. It’s also why Myla goes insane while mining the crystals that are right at the edge of the region, though the amount of machinery there implies that the crystals were mined even in the kingdom’s heyday. Maybe the King thought that it was safe enough with the seal in place? Clearly, it wasn’t.
Unlike most other things in the game, the Grimm Troupe is expressly from outside of Hallownest, probably by a very great distance. They warp to Dirtmouth instantly when you summon them using something that was set up long ago, somehow; considering the lore, I would not be surprised to see them in Silksong. The quest they give you is a rather tedious task, and ramps up in difficulty quite quickly, if you’re intent on doing it all in one go. I, personally, am not. I’ll get the final stage started, but then put it off for as long as reasonable. The quest has two possible endings and I’ve only ever gotten one of them, and I still want that ending for this particular playthrough. But I’ll give the other a few tries, because it requires winning a very difficult fight that I usually only survive for a few seconds.