I upped the stats of all the goblins, trolls and norkers in the place to make them partially demonic. Centuries of interbreeding has made them them evil, but dumb. The boys cleared out one side of the temple and found the access to the Black Cyst.
They recovered the Lament of Tharizdun, but the mostly Neutral Good party wants nothing to do with it. They have no issue with the legendary 333 gems of Tharizdun.
I am setting Tharizdun up as the next big bad. But not till the next generation. That is the 1st Ed AD&D game I started with the children of these characters.
I printed out the newer symbol of Tharizdun and had it ready. One of the demonic trolls had it on his armor, so I showed it to the boys. After some Knowledge Arcana, History and Religion rolls I announced that they didn't know what it was. My youngest, playing a half-elf Sorcerer/Ranger/Arcane Archer stated "I know exactly what it is. It's a target!!" and he fired two flaming arrows into the troll.
I have to admit, I was pretty amused by that!
They finished the adventure and high tailed it back to Glantri City. They are planning on taking a couple of months break before the next leg of their adventures, but I doubt it will be that long. There is some trouble brewing in Two Lake Vale and strange cloud over the land.