Kellering was a young scientist working on the Hammertong project, who contacted a Mistryl Shadow Guard team in 0 BBY. His voice and manner suggested that he was a privileged product of the Imperial Prime University, unused to operating outside the rarefied context of research science, and he claimed that the project leader, Doctor Eloy, wanted the Mistryl to supplement the Imperial security detail led by Captain Drome.
However, when Kellering took Team Prime Manda D'ulin to meet with Eloy at the project base, they were abruptly attacked by stormtroopers, and the Mistryl leader was killed, along with her comrade Pav D'armon. As the skirmish between the Mistryl and the stormtroopers developed, it was revealed that Hammertong was further guarded by heavy anti-aircraft defenses and an Imperial-class Star Destroyer. Given the strength and scale of the Imperial defenses, is thus unclear whether Kellering's ostensible concerns about the competence of the military guards were genuine.
It is possible that Kellering may have been planning to steal the Hammertong - perhaps with the collusion of some of the other scientists, perhaps for the Rebel Alliance; but at present no real evidence is available beyond records of what he said to the Mistryl. It is not even known what happened to him in the firefight where Manda D'ulin was gunned down, and "Kellering" may even have been a pseudonym.