12-9F5 was a specialized M808B Scorpion tank in service with the UNSC Marine Corps. The tank featured a wider-set track and an enhanced undercarriage, making it ideal for urban warfare. As well as its modifications, the vehicle appeared to have a black chess piece in the form of a knight painted on its front left tread cover.
In 2552, 12-9F5 was assigned to the frigate UNSC In Amber Clad. In November of that year, during the Battle of Earth, the tank was delivered to John-117 in Old Mombasa to assist him in fighting his way to the Prophet of Regret's carrier. The Chief, accompanied by two Marines, used the tank to cross the main bridge leading to downtown New Mombasa, destroying numerous Type-32 Ghosts, Type-26 Wraith, and Banshees along the way. However, he was soon forced to abandon the tank in a highway tunnel due to a set of blast doors preventing the tank from going any further.
- The tank will sometimes appear with an ID of UE8-14 on Easy and Normal difficulties, but will most often appear correctly in Heroic and Legendary. The reason for this is unknown.
- Some of the tanks used in Halo 3 multiplayer (via Forge) bear the ID "12-9F5". However, the chess decal is replaced with a Scorpion decal, and is a Halo 3-era Scorpion (with a separate seat for a gunner). Thus, it is unlikely that they are the same tank, although the tank could have had an overhaul.
- It is possible to drive the tank past the barricade in the tunnels with a Warthog and a little patience. However, you will soon be forced to abandon it anyways, as you have to go into the sewer system to advance to the next area.