My oft-delayed Tuesday game has resumed, run at the local boardgame cafe. (In fact, we're the only rpg people there; the employees know us as "The D&D Group.") My two players and their secondary characters (human monk and dwarf fighter) continued to explore the Tower of the Astromancer. (Which is really just Jim Raggi's Tower of the Stargazer run from memory with me making stuff up for the rooms I don't really remember) They discovered the Astromancer, trapped within his binding circle, and foolishly released him. When he ordered them out of his tower, they quickly obliged. They subtly tried to warn the Mage's Guild in the Keep about what had transpired.
The PCs searched about for rumors, coming up with a couple. They correlated two of the rumors (people are going missing inside the Keep, and a group of stonemasons discovered an entrance to the forgotten Undercity below the Keep) and decided to go a-delving into the forgotten tunnels below. We left with them several chambers into the Undercity, having recovered a map that looks like it points to something northeast of the Caves of Chaos on the Borderlands. Will that be their next stop?
Meanwhile, the PCs in the "main" campaign have stumbled across a different entrance to the same Undercity. Is it possible the two groups will encounter one another? That would be pretty awkward. I think I have a contingency plan sorted out, though. We'll be continuing the main campaign this Saturday evening.