| I'm new to this trhead and loving it (so much in fcat that I am about to be late for work- good thing I am the boss). It seems a lot of discussion has been spent on what happens when characters level up, but don't descend deeper into the mega dungeon.
I think I would handle this by converting wandering monsters into static encounters in a way that brings level appropriate encounters to the PCs without breaking believability.
For example as the PCs are working to purge the first level of the dungeon, increasing numbers of monsters from the second level of the dungeon will come up to see what is going on (and why there easy food source is so quickly becoming depleted). Likewise, even larger numbers of those second level monsters might descend to the third level of the dungeon (again, perhaps, in search of food).
This creates a situation in which second level encounters start coming to the PCs on level 1. The PCs then find a level 2 that is mostly deserted (except for nasty traps without treasure) that serves to spur them on to level 3 (which hopefully is level appropriate at this point). Finally, level 3 has been reinforced with a few larger groups from level 2 that, because of their increased size, are hopefully appropriate challenges for the characters.
Chad | 
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