Note: I've called these cults "societies" as a way to distinguish them from the Orders of the Imperial Cult and the random cults and minor deities. I think it better represents the more political and social role these cults play in the lives of their followers.
THE POPULAR SOCIETY OF BULLS: THE MORI-ETAR
The spirit of prosperity, virility, fertility and defense of the realm. The oldest and most widespread totem society in the Niben, predating the Marukhati and in many ways the instigator of the totemic phenomenon. The Bull is most popular among the Niben's rice farmers, where often entire villages are members of the society. Virtually everybody in the Nibenay is involved with the Society of Bulls in some way, although many of the upper classes find him beneath their standing. A conservative spirit, allies to the cause of the Emperor and in opposition to what is seen as the perfidious influence of the court, administration, Elder Council and local rulers. The Bull Society is most popular in the farmland surrounding the Imperial City and towards Cheydinhall.
The most famous tradition is that of the village bull: the strongest and most beautiful bull of the village is chosen as its defender, decked out in gold and jewels, posted on the best fields, and cared for by the community as a whole. If the village suffers some terrible misfortune, however, the bull may be sacrificed and an elder will try to read the portents in its remains. Urban neighborhoods practice a similar tradition, using a wooden bull or a painting of a bull in a prominent location. Gifts and sacrifices are placed at the foot of this image, and if the neighborhood suffers misfortune, the image is defiled.
The Bull cult has close ties to the small, but powerful Priesthood of Morihaus in the Imperial City.
The Hour of the Bull is noon. (each society having an "hour" is something that could influence quests, blessings etc., and plays into the low-key approach these cults would have. 90% of the time the priest of the Bull is just some random guy, but when you visit him at the right hour a set of equipment is added to his inventory and he is decked out in an imposing Bull mask and robe and his dialogue is different. A nice detail, at the least).
Note: I made the Society of Bulls a rather low-grade farmer's cult, which in hindsight might not match well with the divine aspect of Morihaus. Still, if we elect one cult as more sacred and privileged, I think it should be the Dragons.
THE POPULAR SOCIETY OF MOTHS: MIITH-ETAR
The spirit of history and the dead. Popular among storytellers, scribes, scholars, silk-weavers, and morticians. Adherents on the whole prefer moth-burial. Like the Bull cult, the Society of Moths predates the Alessian Reforms, and grew as a public alternative for the exclusive Cult of the Ancestor Moth.
The Moth Society has a particular fear and revulsion for Moth-Eaters, and will persecute those whom they believe are guilty of this crime.
The Hour of the Moth is the evening.
THE JAGUAR SOCIETY: HARN-ETAR
Spirit of cunning, prowess in battle and the hunt. Popular among young warriors, mercenaries, lower ranked Fighters Guild members, Battlemage aristocracy (who do not have ties to the Tsaeci, see the Syff-Etar) and legionaries. In the south-west, the cult is unpopular due to Khajiit association. Known for a specific ritual, called the Citizen's Hunt: once a year, the leaders of the cult come together, select a specific quarry and hunting ground, and invite a selection of the most famous hunters in Cyrodiil to compete. The Jaguars are almost completely free in the selection of quarry and grounds, which has lead to some bizarre situations.
The Hour of the Jaguar is the morning.
THE SOCIETY OF TIGERS: CUCR-ETAR
An obscure branch of the Jaguar Cult, though they claim to precede them. The Tigers operate from within the Jaguar cult and select their members in secret. The tiger is long extinct in the jungles of Cyrodiil, and the Nibenese consider it a mythical creature with strange and dangerous powers, comparable to a dragon. The Society of Tigers also has its own exceptional hunt: their quarry is the winner of the Citizen's Hunt.
The Hour of the tiger is four o'clock at night.
THE SOCIETY OF SNAKES: SYFF-ETAR
Popular among the Niben's aristocrats and upper-class. Connections to the Fighter's Guild (the Syffim) and to the Tsaeci ancestry of many Nibenese noblemen. More influential and shadowy than most. They are said to have a certain connection to Hircine, and his failed were-crocodile experiment.
THE SOCIETY OF FISHES:
The Society of Fishes is exclusive to the Niben's poor fishermen. It has a certain rivalry with the farmer's Society of Bulls, though in all aspects the Fishes are inferior.
THE SOCIETY OF NIGHT-BIRDS: LAR-ETAR
A minor society, popular among thieves and with connections to Nocturnal and the Nightingale Cult. Illegal.
THE SOCIETY OF PYGMY-TROLLS: RUT-ETAR
A minor society, popular among bandits and a more petty, unprofessional kind of thieves. Draws its inspiration from the bad reputation of Pygmy-Trolls (a kind of small, thievish monkey, rumored to steal children from their cradle). Illegal and somewhat repulsive.