Rise of Darkness
There are two types of cults. Revealed and Hidden.
Revealed cults consist of worshipers who knowingly pay homage to one of the Lords of Hell. Usually these cults still operate in secret, as devil worship is frowned upon at best. Asmodeus holds the monopoly on revealed cults, though almost all Archdukes have a revealed cult following.
In order of most to least prominent:
The Cult of Asmodeus: