The con is over and the games went well. Here is a brief report for those interested:
On players and PCs: There were 5 or 6 players for every session. One player played all 4, and another played 3, and one played 2 sessions. Everyone else was a one off. 3 characters were played every session, and all 3 of those leveled to 4th for the final session. They included a goblin wizard who was very hot and cold on magic, a plague doctor, and a priest. Other characters played multiple times included a Knight of St Ydris, a half troll pit fighter, and a sea wolf. There a LOT of carousing after each adventure was complete.
In session 1 the party explored the "greek" themed Axe temple. They made friends with the cultists and ended up fighting the manticore and winning with only one character killed. they killed half the harpies and drove the others off. They acquired a magic battle axe and a suit of armor in addition to minor items and gold.
The second session they explored the Obelisk after a brief and bloody random encounter with a troll. generally, I only allowed for a single random encounter, just because I wanted sessions to focus on the small dungeons the party chose. This adventure felt very Gamma World with the players being good sports about their characters not understanding the high tech stuff that were essentially screens and laser turrets. They did not actually attempt to descend into the black hole powering the place, but it was close. The goblin wizard vowed to find some sort of magic to be able to translate the alien language and return, but they never did. Mostly the took as many "obsidian plates" as they could and sold them. I actually planned to have a rival adventuring party be there if the players did return.
For the third session the players explored a ruined village, which looked like it had been razed -- except for a small monastery at its center (dedicated to cider making monks). Inside they discovered a magical ritual that protected the place from fire (to the point they could not light torches inside; luckily the goblin's light spell worked this time). The undead skeletons of the monks were still performing the ritual. One exploration, the PCs found that there was a secret, corrupt monastery beneath this one (the likely reason why the town had been razed). It was haunted by the ghosts of the long dead monks, and they also discovered a succubus that had been stuck in a summoning circle for centuries. One PC foolishly let her out and was dragged into Hell for his efforts. Good times. They did not go in to the chamber with the Elder Thing the monks worshipped, but they would in the final session.
That final session saw the PCs head to a remote point on the map that previous information suggested was tied to the alien obelisk. They discovered very ancient menhirs etched with multiple sets of runes, including some in the alien language. They were able to translate some of them (not the alien language though) and get the idea that this place was the anchor point of the whole valley on its travels through the dimensions and parallel worlds. It was also guarded by the crabstrosity, and they decided they did not want to fight it and left. ugh. They picked a feature on the map I had not detailed yet so I called for a short break and rolled on some Shadowdark tables. In 5 minutes I had a new adventure in a gnome diamond mine where the party encountered a mutant bullette things. The sea wolf got swallowed and nearly died but was able to cut himself out and kill the monster. There was still a little time left, so they went back to the corrupt monastery and fought the elder thing, which tore the sea wolf in half.
In all a great time and a great group of players. But as usual i was exhausted by the end -- I'm getting too old to run 16 hours of games in 2 days.