Black Knight of the Iron Sphere — E.E. "Doc" Smith

THE GENGHIS KHAN OF THE GALAXY...

Sent on an espionage mission by the elite Corps of One Hundred, Tedric joins the space crew of Fra Villion, history's most powerful and diabolical pirate, pillager of planets, murderer of a hundred thousand humans and submen. Accompanied by two vengeance-crazed men and a traitorous, deposed emperor. Tedric confronts a double challenge: to annihilate the Biomen, Villion's tyrannical race of superhumans, and to keep Earth safe from Villion's ultimate weapon, the deadly Matter-Scrambler, which would destroy the world.