Omega Arsenal

The Omega Arsenal was a collection of forbidden weapons locked in the Time Vaults on Gallifrey, (TV: The Day of the Doctor) beneath the Capitol. (PROSE: The Day of the Doctor, A Brief History of Time Lords)

Rassilon locked the Moment away in the Omega Arsenal after he deployed it against the Nestenes. (PROSE: Pandoric's Box) It was kept in the deepest time vault, Time Vault Zero, for billions of years. (PROSE: 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), the Orphaned Hour (COMIC: Strange Loops), 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 on the final day of the War. (TV: The Day of the Doctor)

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