Okay, so this is something that has been on my mind fora while now. Now that it is 2021 I must naturally share it.
Each tier of Skeleton Key (Wooden, Stone, Gold) seems to encompass a certain arc of the world. Wooden Key bosses are found in Arc 1 worlds, Stone bosses in Arc 2, and Gold bosses in Arc 3 worlds. This is true for just about every Skeleton key boss (With the exception of Simon the Sayer.)
This leads in to my idea. Now that we are in the fourth story Arc of the game, shouldn't it be natural that Skeleton Key bosses in Karamelle and beyond have a new tier of Skeleton Key? It seems only natural if we are following this way of progression. Perhaps the new tier should be Obsidian Keys, like in Pirate101? Or maybe Platinum, or Crystal?
Okay, this is a very interesting question. One is suggesting Candy, another says Obsidian (created from lava), platinum (ultra rare reagent/mineral), then crystal (a substance formed out of minerals).
Since Karmelle has been release and includes a Rock Candy Mountain, how about a Rock Candy Skeleton Key that would be used in a Rock Candy Skeleton Lock and both shatter upon use?
The only conundrum I have is trying to picture what shape the key would appear as since crystals are many shapes. I remember making my own rock candy as a child using a simple syrup, string, glass and pencil.