That Alex Severus is employed by Inquisitor Sicarius, is certain. What is exact role is however, is far from clear. He often acts in a diplomatic capacity, but his arivial is seen by members of the administratum as an ill omen. Quite what his qualifications are is unknown but the aging old word smith seems to have a way of communicating his demands to people and he always gets results.
It has been noted that some of his more intransigent adversaries have not enjoyed the settlement they receive from the Imperium for too long before meeting with an accident. No-one has raised this with Severus and for their sakes that is a good thing.