Omega Arsenal

The Omega Arsenal was a collection of forbidden weapons locked in the Time Vaults on Gallifrey. (TV: The Day of the Doctor) The Tear of Isha was kept in the Arsenal, (PROSE: Engines of War) as was a weapon capable of generating a Null Zone, (AUDIO: The Heart of the Battle) and the anima device. (AUDIO: A Thing of Guile) Over the course of the Last Great Time War, the Time Lords used all the weapons in the Arsenal against the Daleks except for one: the Moment. This was stolen by the War Doctor in the final day of the War. (TV: The Day of the Doctor) The Moment and other weapons were referred to in The Day of the Doctor as the works of the Ancients of Gallifrey.

Behind the scenes
The "Fourth Dimension" feature on the BBC's Doctor Who website suggests that the Omega Arsenal is a reference to Omega.