Rieff was an SCV pilot and general computer whiz in service to the Terran Dominion.
Biography
Rieff served the Dominion by piloting an SCV, his service getting him acquainted with thor pilot Sandin Forst. Rieff became the closest thing to a friend in Forst's mind, his ability with computers proving useful to Forst's personal and often illicit activities. As such, although Rieff could have risen to high level computer-ops, he "adjusted" his military status to remain an SCV pilot, given that Forst's activities paid him better than what the Dominion could offer.
The Jacobs Installation
One such operation occurred on Mar Sara. Alongside Forst and Garth, Rieff was dispatched to the planet to help the Dominion cleanse the zerg from the planet. Forst had other plans in mind however, namely leading a heist of the ruined Jacobs Installation in order to retrieve a cache of ardeon crystals. By threading the group's computer signals, Rieff ensured that their activities would go unnoticed by the Dominion High Command. Given Rieff's computer skills and Forst's firepower, the group reached the installation without a hitch.
They were surprised by automated defenses, which killed Garth. Forst offered to split the treasure two ways with Rieff. Further inside, they discovered a thick paristeel vault door. Forst wanted to destroy it but Rieff advised him that such action could destroy the treasure. Instead, Rieff hacked the computer system to open the vault door. At this point, Forst considered Rieff expendable and killed him.
References
Knaak, Richard A. and Naohiro Washio. "Thundergod." In StarCraft: Frontline: Volume 1, pp. 48–93. Tokyopop, August 1, 2008. ISBN 1427-80721-3.