they devised a plan to kill Mugdulblub and pulled it off. In one room there is a bowl of teeth and ash with a pearl hidden inside; when the pearl is removed, the teeth and ask knit into a skeleton that serves the pearl-holder.
In the adjoining room, there was a +1 dagger that deals 1d100 damage to anyone who tries to take it from it's previous possessor, dead or alive. One PC previously died trying to pick it up!
They had the skeleton pick up the dagger, and it burned him to ash. The PCs swept up the ashes into a shield, placed them back in the bowl, replaced the pearl and removed it. I said that the ashes knit back into the skeleton, as I thought it was clever and the adventure didn't say it could only be done once. He was now able to pick up the dagger safely, as he was still the owner.
Mugdulblub, the Elder Ooze, desires to dissolve the universe and was getting bored with consuming halflings and catfish. So the PCs offered the dagger so it could consume powerful magic. When Mugdulblub took the dagger, it inflicted 53 points of damage -- but it had 58 HP.
The Elder Ooze was a level 12 monster. 3 attacks per round at +8, 2d8 damage. There were also 7 of its servants in the chamber. Within 2 rounds, all of the PCs but one were are 0 HP, and the one who wasn't had 1 HP remaining. It looked like a TPK. The PC made one last desperate attack and rolled a natural 20, killing Mugdulblub!