Anyway, here we go. The Doomguard is the last demon we'll discuss on Demonology 101. Lazy Warlocks such as myself can luck out on a Doomguard with Curse of Doom, our favorite spell on Netherspite. It's a fairly low percentage to spawn one, and Curse of Doom needs to deliver the killing blow on the mob... which can be a long wait considering the curse only deals damage at the end of one minute.
[UPDATE: Curse of Doom has been revised to spawn a Doomguard 100% of the time if it delivers the killing blow! Ritual of Doom also no longer kills a player but damages them, apparently with a Curse of Doom-size damage spell. Doomguards remain enslaved for 15 minutes and disappear thereafter, eliminating the need to enslave.]