The Black Pope
by Mark Ramsay (Jon Maddox Roberts)
1982, Signet
Draco Falcon and his mercenary band stumble across the Black Pope in the pagan backwoods, one of the murderers of Falcon's father now runs an unholy order of knights who worship Baphomet. The order terrorizes small villages, gang raping boys in blasphemous sacrifices before eating their flesh.
Falcon is captured, escapes, hooks up with a pagan priestess, organizes a village defense, and leads a castle siege. We also get some flashbacks to Falcon's time as a galley slave where he endured years of sexual abuse. Between the PTSD, malaria, and being struck by lightning, Falcon regularly snaps into a berserker rage until he his calmed down.
Excellent, but too short. Each segment could be three times longer, especially the siege.