Tacitus
Tacitus, in the Tiberium story arc of the Command & Conquer series, is an extraterrestrial data storage device containing information regarding Tiberium. It appears in Tiberian Sun, Tiberian Sun: Firestorm, Tiberium Wars, Kane's Wrath and Tiberian Twilight. Before Tiberian Twilight, it was a MacGuffin, a plot device to spark more conflict between the already warring factions as the player was required to capture or secure it. Nod and GDI both said that it was a crucial source of information about Tiberium but it did not have a tangible impact (indirect or otherwise) on the conflict at hand. In Tiberian Twilight, however, Tacitus is used to build the Tiberium Control Network to tame the Tiberium and eventually reverse its wildfire growth.
Tacitus is shown in the intro video of Tiberian Twilight; it is an orb roughly the size of a soccer ball. It is named after the Roman historian, Tacitus.
Read more about this topic: Tiberium