Some variant cults of the Demon Prince Orcus rolled created using this blog post of mine: Use Super Heroes gimmicks to create Cults.
Undead: this cult venerate a undead version of their deity. Some believe that the original deity came back from the dead, some believe in a undead double that oppose the original deity.
Cult of Rotting Orcus: this secret cult believe that Orcus physical form was slain in the material plane and that while Orcus' demonic essence reformed in the abyss, his carcass gained a will of it own and is trying to craft it own scepter out of undead tissues. The cult believe that their necromantic art will enable them to control this manifestation of Orcus as it raise in power.
Usurper: this cult believe that a other deity stole the powers or the name of their original deity. Some hope for the return of the original deity, some work against it.
Cult of Orcus Executioner: the cult believe that when Orcus physical form was slain, one of his generals took over his scepter to avenge him while his essence reform in the Abyss. This new Orcus appear as a Balor demon wearing a executioner hood adorned with a ram's skull. Some believe that the Executioner should replace Orcus and are rising hooded undead warriors in his honor. A secret splinter believe that the Executioner went too far and should return Orcus's scepter so that his demonic essence reform faster in the Abyss.
Pet: this cult believe that the deity have a pet with a similar set of power. They believe that this pet is the herald of their deity and that it can intercede for them. They also believe that sometime divine pets work together to secretly protect humankind.
Cult of the Carrion Ram: this cult worship a undead ram that is said to whisper to Orcus the prayers of those who wish for unlife. They also believe that making of blood offerings of horned animals to the Ram can protect them against undead. Some even believe that the Carrion Ram sometimes become a undead white ram, know as Ghost Ram, that join force with other divine pets to defend humanity against invasions from titanic extra planar animal monsters.
Gender switched alternate: this cult believe in a gender switched alternate version of their deity that replace the original deity. (Or that their deity actually changed gender or was actually of a other gender).
Cult of Orcusrella: this cult worship Orcusrella (also know as Orcella), the cruel daughter of Orcus, queen of vampires. Orcella is often called upon by undead women as a spirit of vengeance. She is in favor of The Executioner cult, hoping that he will defy her father when he will return. She wield her own scepter of dead that was crafted for her as a gift by undead dwarfs women.
Divine Spouse: this cult worship the divine spouse of their deity. Those cults are often alternate or lost continuity cults. Some wish that the divine spouse would lead his or her own pantheon.
Cult of the Mourning Mother. Wearing a funeral veil and often accompanied by the Carrion Ram, the Mourning Mother is a mortal woman that married Orcus after refusing his gift of unlife. She throne beside him in the Abyss and gave birth to Orcella with a drop of Orcus blood. She feel a lot of compassion toward undead and lost souls. The cult think that the Mourning Mother and her daughter come from a reality rift that opened in the Abyss when Orcus was slain in the material plane. They hope that their worship will anchor her existence and make Orcus remember her when his essence will reform in the Abyss.
Noble Alien Paragon: this cult worship a utterly alien but noble version of the original deity who is often a legacy upholder or a temporary holder of power.
Cult of Orcellion. Orcellion appear as a muscular ram headed androgynous humanoid, they have three eyes and wield a scepter adorned with a alien skull. Orcellion is the defender of people who became undead to pursue heroic goals. Their body formed in the Abyss when the Mourning Mother's reality rift closed down. Orcellion remember Orcus as a comrade of arms and don't understand why demons are chaotic evil or the concept of alignments.