I've posted the key (in both Word and pdf formats) on the Patreon Page for the elfin prison. I've also given it a new name... the last one was a little clunky. It is now the Elfin Prison at Chancel's Root, which is both more accurate (since Chancel is a huge tree, and it is buried into the root system of the tree), and a little cooler sounding. It's your classic win/win. I've posted this one for free, so that everyone can get it... the next few levels will be for patrons only. So, while you're on the Patreon page, you may as well sign up as a patron, and you could get regular updates of awesome stuff like this, too!
As with everything for Saga of the Splintered Realm, it is released under a Creative Commons Share-Alike Attribution License. The world is your oyster and all of that.