I was considering my campaign plans this week and came up with the idea of using Levistus - the arch-devil frozen in a giant block of ice who rules Stygia, the 5th layer of hell - instead of Adimarchus. I was never a huge fan of the Adimarchus storyline, as I am pretty sure my players wouldn't be very interested in his history/motivations. But an arch-devil? One of the infamous layers of Hell? That's got some potential.
Levistus has a plan of using Cauldron's unique environment to parallel his own, as part of a powerful ritual in which his forces would a) flood Cauldron, killing thousands of people in the process, all in his name; b) freeze the now-flooded caldera, creating a massive lake of ice infused with evil and suffering; and finally c) cause the volcano to erupt, shattering the unholy ice, causing a similar chain reaction in Stygia and freeing him.
Drakthar's Way / Flood Season
Drakthar steals the decanter of endless water from Orak, sells it to Triel, Skaven and Tarkilar. The trio also steal the wands of control water and plan to use them with the decanter to flood the city. When the PCs find Triel (a Paladin of Bane in my campaign, which is 4E) they find a small statue of Bane in her quarters in the middle of a simple bowl of water...odd, but not really noteworthy. When they find Tarkilar, who has the decanter, they find him in a cavern deeper underground and he's got the decanter open in the centre of the cavern, causing it to be semi-flooded. In addition to his T-Rex skeleton, he also has some chillborn zombies and ice attacks, continuing the ice & water theme.
Future Objectives:
• After this "flood, freeze, and blow up Cauldron" plan is thwarted, I want to revert back to the original plot of the Cagewrights rounding up all the Shackleborn and doing the big evil ritual. How exactly this happens is still undetermined.
• I still plan to use the Cagewrights, as the symbolism between birdcages and Levistus in his prison of ice is just as strong as Adimarchus in his cage.
• I also still intend to use the "madness" hooks (Zenith and Alek going mad and whispering prophetic threats, etc.) because I think that's totally in line with something one of the arch-devils would do, and plus I could easily see Levistus as being half-insane after his forced imprisonment for thousands of years.
• Ideally the campaign will end at or near 30th level (again, 4E!) with Levistus (or his avatar) appearing/emerging out of Crater Lake, and having a huge-scale battle with the PCs with possibly other Cauldronites helping / hindering them.
Any feedback, potential problems, or suggestions to offer? Obviously this is pretty rough and not fleshed out completely but I'm open to any ideas!
The only potential problem I see is: how will you tie Occipitus to the plot? If you find an answer for that question, then things should be fine.