I heard that Old Cob is going to be the next villain in the game after Malistaire and Morganthe. Polaris has a sort of weird ending, being the only world where you don't report back to Ambrose at the end. I wonder what they're going to do with that? Anyway, what we know so far is the Old Cob was one of the primal beings of the First World, along with Bartleby and Grandmother Raven. Old Cob is the embodiment of shadow, Bartleby of balance, and Grandmother Raven of light. Old Cob was locked away by Grandmother Raven, but must be kept alive for light cannot exist without shadow. Now, Bartleby has somehow been made sick by Old Cob and we are tasked with finding a cure. Since we did not find this in Polaris with all that Rasputin nonsense being a diversion, we will probably find it in the next world, which will almost certainly be Mirage. But what after Mirage?
Idea1: The game-makers could easily take the easy way out and make the next world after Mirage Empyrea. It would be some kind of Roman-themed world in the sky...(maybe a fuller version of Aquila?) I don't see any way of using Grandmother Raven here though.
Idea2: The game-makers could also make a Grizzleheim expansion that ties the two plots together. Maybe Old Cob and his minions are attacking some part of Grizzleheim and you need to defend Grandmother Raven or something? Sounds like a good idea.
Idea3: Old Cob mentioned something about the Broken Shores back on Khrysalis. There's a very obvious answer if we're looking for something broken to use: the ruins or otherwise whatever's left of Azteca! Maybe after Xibalba hit, there is a battle for resources between the surviving Aztecosaurs and Avians vs the Jaguars and Monquistans. A sort of warm-blood vs. cold-blood war would be both an interesting idea and a way for Old Cob to take something he wants from the planet...maybe an Aztecan artifact of Morganthe's from a while back that can open a portal to the Shadow Web? Who knows what they could do with this!
Idea4: For the final world here, how about Old Cob uses his Shadow Web portal he gained from the Broken Shores to tear a hole in the dimension in Ravenwood (the only place besides Khrysalis of both light and shadow) that leads to the final world: The Shadow Web itself. Unlike other worlds, it is not accessible from Bartleby. It must be accessed from Old Cob's portal. Since Old Cob is a primal being and killing him would disrupt the balance of the spiral, you, Grandmother Raven, Bartleby, and The Council of Light (with a few new members from worlds old and new, including Alhazred, Valgard Goldenblade, King Artorius, Axaya Knifemoon (who you found in the Broken Shores to be still alive), Baba Yaga, and Mellori) must hatch a plan to defeat his forces and re-imprison him before locking him away in the Shadow Web and sealing the portal out so that he will never escape and threaten the spiral again, but will be kept alive for the sake of balance.
Grizzelheim already has an extension: Winter tusk. The hidden lands and the broken shores sound like a place in world rather then a world it'self. Baba Yaga also explained that Bartleby will shortly recover. I am guessing that Empyera and Mirage could be possibly be 2 worlds that KI could create. Aquila pretty much summed up all Greek mythology themed things. I don't think that Empyrea would be a Greek mythology world if KI decided to make one. I don't think KI will do another Aztecan themed world for some players might find the world boring having to defeat more Aztecanthemed creatures and probably have to do quests in Aztecan themed places. I do like your idea with the whole 'tearing a hole in Ravenwood
