4)
This is where Irenicus has set up shop. You can walk by him as you go about killing off the parasites, he doesn't seem to notice. I used the Ring of Ram here and a scroll of time stop. It still wasn't easy, but he went down. One thing to note, if any of your people die in this fight, be sure to either grab their equipment or resurrect them and re-equip them, before you dispatch Irenicus. Otherwise, when you defeat Irenicus and get sucked down into hell, that person will be naked.