Greyhawk zombie outbreak article last week, and I hope to do more articles tied to maps again. Anyhow, today I'd like to follow that up with some commentary on what I see as an intriguing theme within the setting, and that is the prevalence of undead in the Flanaess (nevermind the abundance of demons). Perhaps I've always known this but never really pondered it until I took the zombie apocalypse to an extreme and then combined that with a lich article I did recently. When you look across the breadth of Greyhawk canon, undead are everywhere.
Iuz the Evil, City of Skulls, The Marklands: The Empire of Iuz is rife with typical orcs, goblins, ogres and yes demons, but the forefront of his battle lines is skeleton and zombie armies raised by his clerics. Iuz's symbol is a grinning skull, and his capital Dorakaa is "the City of Skulls", yet he is a demigod of evil, deceit and pain, not implicitly a death god. The fact he employs demons makes sense given his parentage, so mastery of the undead is something he must've learned on his own. Iuz's other necromantic feats include the unholy bone road, bone constructs like the Thassaloss and various magical skulls, wands and staves of necromancy used by his Boneheart henchmen. All this undeath in his culture makes me wonder why humanoids dare work for him.
Ivid the Undying, From the Ashes, Greyhawk Wars, etc.: House Naelax were once known for treating with demons, but once Ivid was turned into an animus, the fractured Great Kingdom went total undead theme. Death Knights suddenly are part of the fabric of Aerdy's history as well, though they are created by a demon prince, Demogorgon, and not Orcus as you'd assume (some kind of demon-undead feedback loop).
White Plume Mountain, Tomb of Horrors, Ravenloft, Crypt of Lyzandred the Mad, Vecna Lives, etc.: Liches as I've presented earlier are heavily invested in the Flanaess. Vecna and Acererak are the prime candidates, but others inhabit Oerth or once did such as Azalin the main rival of Strahd from Ravenloft and Dragotha the dracolich. They are everywhere in every corner of the Flanaess and beyond.
Lost Caverns of Tsojcanth, Iuz the Evil, Vecna Lives, White Plume Mountain, etc.: Vampires aren't as prevalent n Greyhawk, and that's a relief since powerful undead are in such numbers. The vampires we do see such as Kas, Drelnza or Maskelyne could definitely spread their kind if they chose to. I may explore that possibility later.
Age of Worms, Greyhawk Boxed Set, Greyhawk Ruins, City of Greyhawk Boxed Set: As I demonstrated in my zombie outbreak article, Kyuss alone has the chops to spread undead across the continent. There are other deities besides Kyuss, Vecna and Iuz doing this. Nerull the acutal god of death has followers everywhere like the Horned Society, the North Province and hiding in places like the City of Greyhawk and Greyhawk Ruins. Other gods of evil like Incabulos surely has undead components, Hextor god of war is responsible for the creation of the animus. Then there is Wee Jas, goddess of death and magic. Luckily she doesn't seem concerned with undeath.
Other minor mentions to make; there is haunted hills and graveyards galore in the Flanaess. Ghouls worshiping Yeenoghu are known. The Ghost Tower of Inverness is particularly grim. And I'm not even prepared to speculate on undead in the Temple of Elemental Evil and Maure Castle. Basically, the World of Greyhawk is one more major deity or lich away from being the World of Darkness (trademark). Throw demons, devils and Tharizdun cultists into the mix and this setting is much, much, MUCH more evil than Ravenloft.