 Who are the Karna?
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. The trouble was that the Karna had a reputation for losing wars and winning at the peace table. The Karna considered this to be fully neutral territory, and Earth couldn't argue the point very well. It wouldn't have been a problem at all if Earth and Karn had fostered the only two intelligent races in the galaxy. If the Karna played their cards right, their side would be strong enough next time to win. So Earth had to get a delegation to meet with the Karna representatives within the three-day limit or lose what might be a vital point in the negotiations.
 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.