It is unknown what the original purpose of the Chronos was, if that was even it's original name (as it may have been renamed when it was captured by rebel forces), but it is likely that the Empress intended it to be a replacement flagship after the loss of The Gauntlett in the first battle of The Impossible System. This would explain how the rebels were able to make it travel through time so easily if there was already such technology aboard. It is revealed that the ship was built on top of an asteroid, which is where it draws it's gravity from. This asteroid was actually originally a part of New Gallifrey as it is made from Stone Oak, a mineral found on that planet only. The alien attackers would later illustrate a deadly reaction to this substance. The asteroid would also provide a safe