A few more notes on yesterday's session:
MVP Voting Unsealed: MVP and +1 character point in the end went to Borriz, because he pushed for sending the servant wearing the black hat to touch the altar. He thought it was the key, but instead it merely got the disguised monster revealed and destroyed.
Exploration: My players have now reached or touched up to possibly 8 different levels or sub-levels, maybe even 9, including the surface ruins, depending on how you count and what of the places they've found are really levels, sublevels, or just different sections of existing levels. There are a lot more places they can go.
Bulldozing: The PCs have recently been cleaning up on the monsters without too much harm. Some of it is relative power - the PCs range from 300 to almost 400 points, and have been spending a lot of time up near the surface. That's where the much-less dangerous slimes, reeks, spiders, rats, scorpions, orcs, hobgoblins, gelatinous cubes, slugbeats) and so on are. There were more dangerous foes (wights, gargoyles, toxifiers, trolls, two ogres with some friendly gnolls and ape allies, some cultists) but those have been, for the most part, dealt with.
They've done some deeper pushes, and hit a few really hard slogs - the lizard man fight, the draugr, the wizard and his corpse-golems, some moderately hard fights where their firepower prevailed (the hobgoblins/siege beasts, the ropers) - and some fights they cleaned up on due to good tactics or appropriate magic (the fire-men, the ash spirits) or just sheer firepower (most of the rest).
They've also avoided the really nasty fights once they've realized with wasn't an easy kill and easy money - the draugr, the Lord of Spite (although they often plan to go after him, they haven't yet), the wizard, and a few others.
They are extremely, extremely prepared to dice up living/non-special melee foes. Borriz with Axe/Mace-28, Vryce with Two-Handed Sword-26 and a pile of parries to expend on himself and others, Chuck with Extra Attack and 3d+11 cutting damage and Kiai, etc., plus Galen and his stream of endless arrows. Some other treats are more difficult for them, and they've either dealt with them less well or just moved away from them. Combine that with picking their fights and for GURPS fights to allow for both disastrous defeat or total victory, and there you are.
It's tough to gauge a fight's impact, but I feel like the threat is mostly there. My experience has led me to change some as-yet-unmet monsters to be more or just differently challenging, of course.
But it's also a good example of a "downside" to megadungeon play, if you can call it that. Since the players can choose where to go, and when to come back, they will avoid the hard stuff and aim for the easy stuff.
Rope: Every adventurer needs some rope, and I need to think of every single trap or encounter in terms of "if they apply enough servants and rope, what happens?" Because they always will - create a noose, have some servants pull on the rope, what happens?