Vortex Code
The Vortex Code was a four-dimensional co-oordinate which led to Chrone, the oldest planet in the universe, where the Code could be used to control an access point to the Time Vortex there, allowing the user to time travel. The Code was stored in a Mark 9 Servitor which was placed in a Starfire cruiser bound for Earth to keep it safe from hostile forces. The cruiser was forced to crash in the Gorlon asteroid field by Stellion Core pirates, but the Tenth Doctor helped the damaged Servitor escape and took it to Chrone. The pirates met them there and demanded that the Doctor repair the Servitor so the Code would not be lost, but the Doctor tricked them by secretly altering the Code so that it would only take them to the top three theme parks in that sector of the galaxy. (COMIC: The Vortex Code)