Unlocking Meteor Horseshoe Farm?

So, pretty much the title. I need a good deal of Horseshoes, and I just powered through Camelot in like five days thanks to the 1/2 AP. The site says that Camelot's "Land of the Void" area is the best place for them, but I don't have it open even after finishing the world. Generally this means that it's hidden behind one of the other Free Quests and needs to be unlocked, but Gamepress doesn't say which Free Quest unlocks it, unlike past worlds. And since I no longer have the grace of 1/2 AP, I don't want to spend the extra days it would take to clear every free quest one-by-one to try and find it that way.

Does anyone know which Free Quest unlocks Land of the Void? I already cleared the Royal Castle and Wastelands of Death (the two most likely ones, imo) to no avail.