The second life of the archmage

Since ancient times, portals have been opening on the ground to other worlds from which guests come. The guests are very different: aggressive and peaceful, possessing many knowledge or not at all capable of communication. Unites their magical gift and the inability to go back.
Vladimir Seversky - a young archmage and an employee of an organization who is tracked by fellow people. He is a gatekeeper, one who first meets guests and should be ready for everything. His weapon is a bullet and magic, behind five years of study, and ahead is an interesting and very unusual career.
But on the first task, everything went wrong. The guest is dead, and Vladimir had an unusual fellow traveler and a whole bunch of problems. As well as the feeling that everything is just beginning