Markko, a Human of the male variety, operated as an Alliance Intelligence operative, but masqueraded as Imperial Counselor Raines. Raines was part of Egron's team on Chibias, and Markko assumed this identity in the time following the Battle of Endor.
It came to Mara Jade's attention that Markko had been employed by Egron with the task of breaching a datacore to then sell intelligence to the Rebel Alliance. Markko, however, couldn't completely bypass the datacore's security, and sought the assistance of Ghent to finish the decryption. In truth, Markko's interactions with the Empire were a facade, as he was an Alliance agent whose mission was to ensure the Alliance obtained the datacore—which was actually the control center for a Star Destroyer.
Despite this, he wasn't ready for Mara Jade's sudden appearance, although he did survive the subsequent escape. Later, along with Governor Egron, he confronted Mara and Ghent. Mara eliminated Egron with a shot to the chest, after which Markko held Ghent as a hostage. Mara decided her task was complete, as she had only come to eliminate an Imperial traitor, and did not want to continue killing. Mara released Markko, on the condition that he release Ghent. Markko complied, and Mara allowed him to depart so he could return to the Alliance.