Onimagi

Onimagi is both the title, and all that is known of the name, of the ruler of the underworld in Bajapur. To outsiders and the lowest level members of the criminal gangs which permeate the underworld, all appears normal; as though all the gangs are completely separate and in competition with one another for control of parts of the city and its criminal underworld. Those in the know are aware the truth is very different. All the major gangs are controlled by one shadowy overlord, with even his true name concealed from those who serve him.
Information about the Onimagi is strictly controlled, and even his lieutenants who lead each gang as its supposed Oyabun, or leader, know little about him. They serve him reverentially, as he has built a cult-like following using his undeniable power and immense knowledge, and follow every order exactly, even willing to die for their lord if necessary. Each tier of the gangs above the footsoldiers knows progressively more about him, but even that is limited.
What is hidden from all is that the Onimagi is a lich, albeit a relatively young one. Three centuries ago as a mortal man he was employed as a combat wizard by one of the gangs in the city. He fought several battles with the footsoldiers of the other gangs and the Golden Hand, the intelligence division and secret police of the Great Tycoon, ruler of the city. Having seen the fate of all those who fought in this hidden war for control, he decided to seek immortality. Being both more cautious and self-aware than others like him who sought lichdom, he researched the shortcomings of the other liches who locked themselves away in their research, only to go insane; and discovered that their common failing was their isolation. So he decided to remain in contact with the outside world, retaining his sense of self and psychic balance.
The wizard rose rapidly in the ranks, attaining his goal of lichhood as he gained the greater resources afforded his position. He soon gained power over the other gangs, secretly consolidating their leadership, and created the beginnings of the cult which would serve him. Even his closest lieutenants are unaware that he is a lich, being trained not to question his apparent immortality.
The Onimagi makes extensive use of the Magic Jar spell to replace his lieutenants when he wants to take a personal hand in the leadership of a particular gang, or ensure that events turn out a particular way. The Oyabun of each gang has a piece of jewellery with a large gemstone which serves as the focus for the spell, and he can take control of them at will. They gladly permit this, as he grants them specialised knowledge and skills in return, while bringing his wealth of abilities into play when he takes a hand. Should the Oyabun happen to be killed in the process, then the Onimagi simply returns to his phylactery, and is reborn a week later to seek revenge upon the interloper.