|Political and military information|
Following the end of the Human-Covenant War in January 2553, he and Beloi went to Sydney to the ruins of the Parthenon Bar to raise a drink in honor of Barakat, as he wished to happen when he died. Later he and Beloi were hand-picked by the Office of Naval Intelligence Commander-in-Chief Admiral Parangosky to serve under Captain Serin Osman in a covert operations team designated Kilo-Five. The team was tasked with sowing discord amongst the now-disorganized Sangheili by a number of means, including providing arms to the Servants of Abiding Truth, a faction opposed to the allies of Thel 'Vadam. 
As part of Kilo-Five, Geffen served aboard UNSC Port Stanley, participating in several missions. These included the extraction of the ONI agent Mike Spenser from Reynes, where Geffen and Beloi were involved in a brief firefight with several Kig-Yar who were attempting to claim the team's dropship for themselves. At one point, Kilo-Five seized the Covenant cargo ship Piety and successfully captured a Huragok, Requires Adjustment. Geffen and Beloi were also present during several arms transactions between Kilo-Five and the Servants of Abiding Truth.
After ONI had established communications with the human survivors inside Trevelyan, Admiral Parangosky ordered Kilo-Five to arrest Dr. Catherine Halsey. Geffen accompanied the party that entered the shield world via dropship, detained Halsey and brought her, along with the other survivors, aboard Port Stanley.
- Geffen's medical zap badge reads "A+/NO V-CIN" indicating his blood type is A+. The meaning of "NO V-CIN" is not clear, however NO may mean "nitric oxide" suggesting he may have at one time suffered from pulmonary embolism or angina.
- While writing Halo: Glasslands, Karen Traviss originally envisioned Mal as being Australian, but later changed his nationality to British.
 List of appearances
- Halo: Glasslands (First appearance)
- ^ Twitter: BTW, re Halo Glasslands
- ^ Halo: Glasslands, page 181
- ^ Halo: Glasslands, page 83
- ^ Halo Waypoint- The Halo Bulletin: 10/12/11, Exclusive Book Excerpt - Glasslands
- ^ Halo: Glasslands, page 387
- ^ Halo Waypoint — 343 Sparkast #5
- ^ Halo: Glasslands, page 28
- ^ Halo: Glasslands, page 32
- ^ Halo: Glasslands, page 67
- ^ Twitter: Mal started in my mind as...