Eppon was the designation given by Tash and Zak Arranda to the baby they came across in Borborygmus Gog's laboratory, which was secreted away on the desolate planet called Kiva.
Tash and Zak Arranda initially discovered Eppon inside a pod that resembled an egg on the world of Kiva. From what they could observe, he appeared to be Human. He was only capable of uttering a single word: "eppon." Tash took this to be the child's given name. In reality, the child was attempting to pronounce "weapon."
The Arrandas were taken aback when the infant began aging at an accelerated rate, transforming into a toddler just as a team representing the Alliance landed on Kiva to investigate Gog's laboratory for details regarding Project Starscream. As Eppon's rapid maturation continued, Alliance soldiers started disappearing one by one. His true identity was only revealed when Zak and Tash encountered Borborygmus Gog, who they had previously believed to be dead. Eppon represented the final stage of Project Starscream and the culmination of the Project's research efforts. Eppon needed sustenance in order to continue his growth. He had, in fact, devoured the Alliance soldiers, assimilating them into his form.
Eppon served as a prototype for Gog's Army of Terror, a collection of genetically engineered weapons that possessed immortality, the ability to shapeshift at will, the power to read the minds of their targets and exploit their deepest fears, increased strength with each consumption, and immunity to the Force; thankfully, this last trait was never fully realized. They were programmed to obey any command issued by their creator. As Eppon developed, a violet mark manifested on his forehead and expanded until it enveloped his entire body with a scale-like armor. As time went on, Eppon, who initially appeared quite Human-like, morphed into a grotesque monster. Eppon almost consumed the Arrandas' uncle, Hoole, before Tash employed the Force to assist him in breaking free from Gog's control. After realizing his fate, Eppon turned against Gog, but Gog activated the fail-safe mechanism embedded within each of his warriors. A small explosive device implanted within Eppon's brain obliterated a significant portion of his body.
The epilogue of Galaxy of Fear: Army of Terror concludes with a near-cliffhanger, depicting the remnants of Eppon's body in motion. Although this implies that he might have survived his seemingly fatal wounds, it has never been substantiated and the text attributes it to the wind.
Eppon shares a striking similarity to the Metaluna mutants featured in This Island Earth.