Which is what Severnus's Frumentarri are. They're spies, thugs, and saboteurs. They function as the left hand of the Emperor to Claudius's right hand. Severnus is made personality wise where he's so dead inside that he is willing to seduce the nun, and then rip her throat out when he has the info he needs to then burn down the church. Claudius has morals, and an army to keep care of so he must rely on the cold Severnus to deal with other people in less honorable ways. You can be a part of another guild. That guild just will likely hold little barring, and the npc's will certainly not respect you for awhile due to your nature.