Although Chzulu is associated with the undead, it is worshipped across races by necromancers who do so in secret because worshipping it is forbidden.
Humans and nomads can certainly be found as members of Chzulu's cult, but no dwarves or elves are ever interested in joining. Demons, who already have their own forms of immortality, do not take part in Chzulu's worship, but do have respect for the God. Chzulu's greatest number of followers are the lizardmen, who built a temple in honor of the God in the northern region of Issanis, north of the Unforgiving Swamps. Lizardmen however, have a much different view of Chzulu than other races. According to Lizardman lore, Chzulu was once a great serpent, with a maw large enough to devour the world. They say he is older than the world by several thousand years, and that he had devoured many worlds in his existence. The great serpent created the Lizardmen as its tools on Aravorn, to prepare the world for being devoured. No Lizardman knows what happened, but they do know that when danger came for their god, they failed. Perhaps Tayrion came for it, perhaps another great force. Regardless, due to the failure of the Lizardmen, Chzulu's form was scattered. The Lizardmen believe that they have lost their god's favor, and seek to regain it by helping Chzulu regain its form. They believe that their worship can help coalesce Chzulu's energy field back into the great serpent they once served. In the meantime, Lizardmen burn all of their dead as a symbol of repentance. Until they have proven themselves worthy, they will not even offer their dead to Chzulu's gifts. In turn, Chzulu will not reanimate Lizardman corpses. Perhaps one day, the Lizardmen will discover the way to reform the body of their serpent lord, and then the world will be awash in Lizardmen Liches
Today, Chzulu will only grant its power to those who are dead. If one has proven their devoutness in life, Chzulu will grant said person eternal life as an undead servant. The servants must obey Chzulu's will, but they are still allowed some freedoms. That's why it's common to see many of the undead fighting amongst themselves for power or survival.
Chzulu's greatest foe is Tayrion, whose power can negate the resurrection of the undead.