Humans bow to different gods, but only one of them has real power and worthy to be considered intently - God of Light, whose church is official church of Empire, and - its heaviest weapon.
Unlike, for example, elven church, who rules over the state, human church serves to Emperor and his interests, supporting armies with its powerful magic.
God of Light is the most mysterious god, he's remote from everything concerned with humans, and only selected ones are able to understand his motives. To communicate with their god, human priests use special science of signs and numbers, allowing to direct his power as necessary. This science, giving great power to church members, known in other nations as Magic of Light - because it has formal similarity with other human magic schools. It's easy to explain this similarity as many hundreds of years imperial mages are under control of the Church and make their experiments and investigations only according to its instructions. The last free magic enclave of Empire - Rainbow valley - fell under pressure of undead more than two hundred years ago, in the very beginning of Great Invasion.
Human magic is one of the most flexible and powerful magic arts of Aivail. Human mages as a rule are not specialized on one magic school; they have knowledge of several school, but not so deep. For several hundreds of years Silverhill - city at the Gates of Thunder - is the magic capital the Empire. All mages in Empire must be registered by Inquisition, so they are under its private supervision. Majority of magic practices are allowed, but some types of magic art - as necromancy - are strictly prohibited by Church. Some places where human mages can study prohibited practices are called Enclaves of free mages... majority of them situated far from territories controlled by Inquisition. Of course, there are exclusions in all rules - for example court necromancer of emperor Julius 3, Holy Ortega, who lived and worked at court.
The most active wing of the Church, persecuting heretics and participating in all military conflicts, is Holy Inquisition. There are different orders in it, each of them has its own specialization. For example, Order of Moon Blade searches for necromancers and fights with undead; Order of Flaming Fist - controls teaching of mages and controls them; Order of All-seeing Eye deals with internal investigations in the Church, searching for heretics among priests.