Insanity Clinic: Library
"So you know that Puzzle Keys have the three rings, Puzzle, Location, and Known," Calano said, looking up from his work, "The Puzzle and Location are self explanatory, but the Known is a bit more complicated. Basically, it's a short sentence or phrase which can give a preview of what you'll find once you make it to the destination assigned to the Puzzle Key. In this case, the Known for the Sixth Archive would be whatever the most common form of knowledge contained inside is. What I have so far is a couple words, letters, and phrases. The letters K, S, and D, the words Power, Growth, and Prison, and the phrase Words to hope. There's still a bit more to uncover though. Does that make sense?"
@Ookla the Perpetual