Capítulo 57: [Gray!]

You probably already know about the Seven Deadly Sins: 

Greed, Gluttony, Pride, Sloth, Wrath, Lust and Envy

Well, [Call of the Black Magicians] have something similar too in this world of Zarraf. In this world, there are 7 individuals who wield the power to control one of the cardinal sins.

That power can only exist in one individual at a time. It can be stolen or taken, or even given away to another by the individual who has it. 

While it sounds all good to have the power to control a sin, it is actually more complicated than it looks like. Each sin's power comes with an individual demon that resides within the individual who holds the power.

The demon grows stronger with the individual and, once with enough power; he fights for the ownership of the body. That is the sole reason the demon gives power to the individual.