All the characters resided in the same shared universe, and the deal also presented the final time that Kirby had complete creative control over any of the many properties that he had created in his career.
As revealed in Jack Kirby's Secret City Saga #0 (April 1993), at some point in pre-recorded history "fifteen millennia before our own", there existed a race of beings known as "the Ninth Men".
As a contingency, the scientific and military leaders of Gazra placed three of their citizens into hibernation, with hopes that these three would survive "the Great Catastrophe" (a term used for these planet-wide storms) to spread the ideals of the society of the Ninth Men onto the next age of Man, which is revealed to be the present-day humankind.
After release from hibernation, they discover and attempt to foil a plot whose origin lay in the last days of Gazra, involving an evil duplicate of then-President Bill Clinton.
Members included: Brian Bluedragon, a doltish knight of Arthur's court; Hard Luck Harrigan, a petty gambler and bookie who worked in the 1930s criminal underworld; Dr. Mordius, a Henry Jekyll wannabe; Kuga the Lion-Killer, a warrior of African origin; Dezira, of ancient Babylon; and Frightful, a demon in Satan's employ whose job it was to keep the members in line, a "drill instructor from Hell", so to speak.
Their job was to intervene should any of the wild (and most times, monstrous) creatures that populate the bowels of the Earth try to attack the surface world (or as they referred to it, "Upworld").