 Who are the Karna?
Every man in the Diplomatic Corps who developed a twitch or a quirk was shipped to Saarkkad IV to work under Bertrand Malloy, Permanent Terran Ambassador to His Utter Munificence, the Occeq of Saarkkad. He trusted no one, and was perpetually on his guard against imaginary plots and persecutions. Number two suffered from some sort of emotional block that left him continually on the horns of one dilemma or another. He was psychologically incapable of making a decision if he were faced with two or more possible alternatives of any major importance. Number three ... No two men were alike, and yet there sometimes seemed to be an eternal sameness about all men. He glanced at the Earth calendar dial that was automatically correlated with the Saarkkadic calendar just above it. And what did he have to show for it besides flabby muscles, sagging skin, a wrinkled face, and gray hair? Out there was the terrible emptiness of interstellar space—a great, yawning, infinite chasm capable of swallowing men, ships, planets, suns, and whole galaxies without filling its insatiable void. Somewhere out there, a war was raging. Somewhere out there, the ships of Earth were ranged against the ships of the alien Karna in the most important war that Mankind had yet fought. He was not in the battle line, nor even in the major production line, but it was necessary to keep the drug supply lines flowing from Saarkkad, and that meant keeping on good terms with the Saarkkadic government. The Saarkkada themselves were humanoid in physical form—if one allowed the term to cover a wide range of differences—but their minds just didn't function along the same lines. To have shown himself to one of them would have meant instant loss of prestige. The Occeq of Saarkkad himself was never seen except by a handful of picked nobles, who, themselves, were never seen except by their underlings. To violate the rigid social setup of Saarkkad would mean the instant closing off of the supply of biochemical products that the Saarkkadic laboratories produced from native plants and animals—products that were vitally necessary to Earth's war, and which could be duplicated nowhere else in the known universe. It was Bertrand Malloy's job to keep the production output high and to keep the materiel flowing towards Earth and her allies and outposts. The job would have been a snap cinch in the right circumstances; the Saarkkada weren't difficult to get along with. A staff of top-grade men could have handled them without half trying. They couldn't be spared from work that required their total capacity.
 The Karna are the second most powerful race in the galaxy. They are skilled negotiators.
 The Karna are the second most powerful race in the galaxy. They are skilled negotiators.  The Karna are a race of warriors bent on destroying the Earth.  The Karna are a peaceful species trying to negotiate a surrender to Earth.  The Karna are a predator race who are trying to invade the Earth, to use humans as a food source.