And here goes some of the groups I created for my home campaign:
Adepts of the Eternal Wheel: this arcane sect originated in Old Thassilion, probably as an off-shot of the mysterious cult of the Peacock Spirit. These monks and mystics believe that is possible for a mortal to ascend beyond the Great Sphere and the gods, but to reach this exalted state they must travel the Path of the Eternal Wheel. The Path is made of the Nine Steps of the Spirit: each step represents an alignment. The Adepts must live at least one year of their lives in each alignment. The Ninth Step would represent the True Neutral alignment. Due to the these harsh requirements, most Adepts either give up or go irrevocably mad. There are rumors of strange powers bestowed and of the servitude of creatures from the beyond the known planes among Adepts of higher rank. Other tales link the mystic sect to the earthbound demons known as rakshasas.
The Servants of the Source: this semi-religious order is readily recognized by the red hooded robes of its members. The Servants are famous for converting “monsters” and barbarian humanoids to the ways of good and order. They happily buy living intelligent creatures and slaves from evil races like orcs and ogres. These creatures are taken to the stronghold of the order, in the lower levels of the city. After a few weeks this creatures return to the world “redeemed” (in game terms: with lawful and good alignments). The secret of the order is that its members keep an ancient celestial bound within its fortress. From the blood of the good outsider the Servants are able, through a harrow ritual, to slowly change the alignment of any creature. The irony is that the Servant themselves are far from good, but believe that their “taint” is a necessary sacrifice. The order was founded by a group of ex-paladins.
Hagga, the Soul Keeper: this night hag offer sinister services, mainly among them the ability to store a part of the soul of any mortal in a sinister green flask. If the soul-giver later dies, all its allies have to do is to carry the body (intact and healed) to the hag for it be revived (as the spell breath of life, but without the time requirement). Other less know service provided by Hagga is the ability to swap souls between bodies. This last ability is usually paid by old nobles or monstrous creatures trying to live among human and other races.
The Brotherhood of the Beast: this group of lycanthropes is a living paradox. They walk openly around the city, clad in hags and bells, to denounce their condition. The Brotherhood works as bouncers and mercenaries inside Kaer Maga. They hunt and exterminate wild and uncontrollable lycanthropes. Rightly feared, they also have a secret agenda: spreading their “Gift” (lycanthropy) to the rulers and leaders of the City of Strangers.