Bronislaw Czevak

High Inquisitor Bronislaw Czevak of the Ordo Xenos walked into the Black Library and made that everyone's problem. Four centuries of service, a vanishing on Darcturus, and a stolen Atlas Infernal later, he was the human Ahriman most wanted alive and the Harlequins most wanted back in a cell.

He mapped Webway paths the Inquisition is not cleared to know, escaped the Library with a pariah's help, and spent the rest of his career being hunted by a sorcerer who had already peeled him once. The Atlas lets him cheat geography. It does not make him popular with the Black Council.

Most Inquisitors collect xenos secrets. Czevak collected the index, then had to keep running so nobody else could read it over his shoulder.