Of the Kiranka clan, the son of the Kilrathi Emperor, father of Ratha and Thrakhath.
Before the start of the Terran/Kilrathi war, in 2634, Gilkarg borrows an idea from a Confederation experiment called the Panama War Game, –which the kilrathi obtained from the onboard computer of a settlers' ship in Fawcett's World, when the planet is taken by the Vakka clan. The experiment showed that, should there be a type of missile able to penetrate phasing shields at high velocity, a carrier based attack should win over battleship-centric warfare. Gilkarg plans a deadly strike using carriers as the leading force.
His plan proves successful during the early phases of the attack on Base McAuliffe.
However, a combination of restrictive imperial orders, misunderstandings between Gilkarg and Admiral Nargth, underestimating of the enemy, failure to concentrate on one target at a time, dispersal of forces, sabotaged equipment, overconfidence, and many other snafus, the kilrathi fleet end up losing most of their landing forces, two of their carriers, two battleships, and several destroyers and frigates. Although the main mission could still have succeeded, the emperor orders the fleet back to Kilrah.

During the Battle of McAuliffe, Gilkarg's son, Ratha, commits suicide, leaving Thrakhath as his only heir.

Gilkarg was ordered killed by his own father, the Emperor, in 2654, for his failures during Terran operation Thor's Hammer, leaving behind his son, Thrakhath, as the Crown Prince.