The second most powerful man made weapon in existence, with the power to theoretically obliterate anything in its path, including a planet. Only one such cannon exists, mounted in to the bow of Dragon.
The Honour of the Knights
The Third Side
The Attribute of the Strong
It was discovered (during a misfire of Dragon's main cannon), that a sizeable anti-matter detonation in the atmosphere of a planet would trigger a firestorm that would engulf the world. It was believed by some that the temperatures caused by the explosion led nuclear fission to occur. Torelli was the first planet to fall to Dragon's anti-matter cannon, around 2620.
The Pandorans made liberal use of the cannon from then on, using it in place of nuclear weapons and mass drivers to destroy entire worlds in a matter of hours. Spirit was the first Helios world to be destroyed by the cannon, its destruction coming shortly after the Pandorans returned to the Temper system.
The allied forces made the destruction of Dragon, and with it the anti-matter cannon, one of their top priorities following the revelation, although they did not succeed in doing so until the Battle for the Solar System, in late 2624, when Dragon was also destroyed.