This is what my gamers would do. An fascinating base of OPs it will make.

The best (?) answer for a marketing campaign is to have the large dangerous clearly as much as one thing for the primary a part of the marketing campaign, getting the data (both from books or taking individuals prisoner) from arcane architects, nice wizards, astronomers, and so on. Then, the ritual to do one thing is clearly shut at hand round stage 9, and there is a hard-fought battle to get into the fortress. Add a ticking clock onto the large battle after which, when it is counted all the way in which down, the fortress takes off, presumably carrying some or the entire participant characters with it, into the environment after which, assuming they cannot take management of it earlier than then, into wildspace.

Those left on the bottom have to provide chase, both to cease the villain from utilizing their now vastly extra highly effective fortress to do who is aware of what. Luckily, one of many partitions left behind additionally features a tower, the place one of many villainous dangerous man’s lieutenants was based mostly, full with notes explaining what simply occurred … and analysis displaying {that a} spelljamming vessel is hidden the place the remaining participant characters can get to it (after an appropriate dungeon crawl, together with some bizarre Spelljammer monsters and the like, to convey that issues are about to be completely different within the again half of the marketing campaign).

Then it is a easy matter of chase after the fortress, slip aboard, rescue the princess different social gathering members, and defeat the villains in command of the flying fortress. But earlier than they destroy it, they be taught that, whereas the villains won’t have been nice, they had been creating the fortress to flee an imminent world-destroying menace FROM SPAAAAAACE and now have to make use of their new headquarters to assemble allies from all through a number of techniques and take the struggle to the alien warlord whose personal even bigger fortress, is at the moment barreling towards their dwelling by way of the Astral Sea.

Anyway, that is what I’d do, as a DM.