Tacitus

The Tacitus was a source of Alien knowledge.

Description
The Tacitus appeared as a spherical object with strange symbols all over it. It contained a vast amount of alien information, "Millions of Teraquads of data," to quote Dr. Boudreau. It was unique as a data source in that it was difficult to read the tacitus while it was incomplete, while it was easy to read once it was complete. The exact mechanism behind this procedure is unknown.

History
Kane had the Tacitus first, having acquired it from an alien ship, it is presumed. Though he knew that it was important, he couldn't translate it himself, and he enlisted the services of the mutant leader Tratos to help him with the Translation. Other than Tratos, Cabal was the only one who assisted with and knew how to translate the Tacitus. Kane used this technology to several important pieces of Technology, such as the Banshee aircraft. More importantly, it also allowed him to create a world altering Tiberium missile. However, before he could use the Tacitus, his temple was overrun by GDI forces, who discovered the Tacitus in the wreckage of Kane's Temple of Nod.

After GDI found it, they had difficulty translating it. However, they realized that it was the source behind the Tiberium missile. At this time, the beginning of the Firestorm Crisis, it was their only lead towards preventing the rise in atmospheric contamination by Tiberium. To this end, they attempted to have it transferred from the Cairo Temple to a GDI research center and delivered to Tratos for decryption.

Before that happened, however, Cabal had Tratos assassinated, and GDI was forced to 'capture' Cabal, and have him translate it. However, Cabal informed them that a second piece of the Tacitus was needed to complete the translation. Once GDI recovered the second piece, Cabal turned on his former masters, intent on using the Tacitus for himself. By the time that the resulting Firestorm Crisis had been dealt with, Cabal had used the Tacitus to create a second doomsday weapon, the incredibly powerful Core Defender. Fortunately, GDI was able to recover the Tacitus.

It was discovered by GDI that, with the addition of the second piece of the Tacitus, no decryption or translation was necessary. It remains to be seen what exactly the GDI will do with the Tacitus.