A Temporal Cannon was a weapon created by the Eternity Circle to be used against the Time Lords during the Last Great Time War.
Characteristics
The Temporal Cannon had De-mat capabilities and could be fitted to a standard Dalek, replacing its mid section. The cannon could wipe an individual from history, although the Daleks made sure to make themselves immune to the weapon though Time Lords and humans, with a bit of effort, could remember the victims. (PROSE: Engines of War)
History
The Eternity Circle planned to create a new paradigm of Temporal Weapon Daleks and spread them throughout the universe through the use of the Daleks' progenitors. The Daleks harnessed energy from the Tantalus Eye to create a Temporal Cannon comprised of three moons to wipe Gallifrey from history, allowing them to finally win the Time War. With the Daleks in the Tantalus Spiral it was destroyed by Borusa. (PROSE: Engines of War)