In the 2290s, Guard Trooper Onn served in a observation outpost in the L-langon Mountains on the planet 40 Eridani A-II. The Interstellar Guard starship IUES Ashoka dropped off a team of scientists and security personnel to study the Eridanians.
In 2293, Guard Trooper Pol kj Onn and the rest of the team were slaughtered by T'Pau's clan. Their bodies had been shoved onto poles driven into the floors. The Eridanians bisected the heads and removed the brain.
When the IUES Kumari II arrived to check in with the outpost, the landing party discovered the team's corpses. Guard Trooper Onn was identified by intelligence officer First Lieutenant Yrrebneddor th'Eng. (ST - Myriad Universes novel: The Tears of Eridanus)