Eisenhorn

Inquisitor Gregor Eisenhorn is an Imperial inquisitor, one of the tirelss defenders of humanity. With his warband he scourges the galaxy, walking in the shadows of darkness in order to root out heresy. When that heresy is found to infiltrate the hierarchy of the Imperium and the Inquisition itself, Eisnehorn must rely on himself alone to deal with it – even if it means making deals with the enemy and compromising everything he ahs ever believed in.

Read it because
It's the whole classic trilogy that remains top of many Warhammer 40,000 fans' must-read lists, And in Pariah, there's a chance to catch up with Eisenhorn decades later, when he's a renegade from Imperial justice...