The stories revolve around the exploits of Casca Rufio Longinus, the Roman legionary who drove the Holy Lance into the side of Jesus Christ on Golgotha.

As a result of this action, Casca is cursed with immortality, and he is to wander the Earth aimlessly, always as a soldier, until the Second Coming.

[6] Some time later, in an altercation with his superior officer over the affections of a dancing girl, Casca is stabbed in the stomach.

He feels all the pain of the many beatings he endures, and is soon covered with scars, but his internal damage heals, often overnight.

Concealing his ability to heal miraculously, Casca rises through the gladitorial ranks, eventually gaining his freedom from Emperor Nero himself.

Eventually he is put on a war galley, and during a sea battle, his vessel begins taking on water.

For the rest of the series, Casca is seen fighting in numerous wars and famous engagements, including Cortez's conquest of Mexico and the battle of Điện Biên Phủ.

Over the course of the series, Casca meets numerous famous historical figures, such as Niccolò Machiavelli, Adolf Hitler, Attila the Hun, Blackbeard, Genghis Khan, Marco Polo, Robert E. Lee, George Washington, and Muhammad, among others.

Julius Goldman was a surgeon in the United States Army with the rank of Major, stationed at the 8th Field Hospital in Nha Trang during the Vietnam War.

The Brotherhood was founded by Izram, a man who proclaimed himself the thirteenth Disciple in the wake of Jesus's death, supposedly as a result of Casca stabbing him with the Holy Lance.

Izram purchased the Holy Lance from some of Casca's comrades as a relic and symbol for the events on Golgotha.

Notable real-life historical figures depicted as elders of the Brotherhood of the Lamb include Heinrich Himmler and Hassan al-Sabah.

A similar popular historical fiction parallel may be found in the Harry Flashman series in which a skilled man-at-arms and rascal raconteur of the 19th Century finds himself in parlous combat in distant lands but always manages to survive to reappear in another novel.

Beginning in 1984, Star Book, a paperback division of W. H. Allen & Company, published The Eternal Mercenary, God of Death, and The Warlord.