A Quake Cannon is the scourge of enemy fortresses across the galaxy. When mounted on the super-heavy Imperial tank known as a Banesword, whose armour is incredibly resilient, it becomes one of the Imperial Guard's most effective ways of breaching a stronghold. Though primarily a siege gun of formidable power, suited to wrecking fortifications, there will be little left of any war engine that finds itself in the Quake Cannon's sights.
It is the ammunition of the Quake Cannon -- the ghoulish Quake Shell -- that marks out the weapon as unique. Each shell contains fragments of a planet that has undergone the ultimate Imperial sanction of Exterminatus. Whenever planets are to be destroyed, Tech-priests and Magos Geologis from the Adeptus Mechanicus are dispatched to the sector to capture and store the shattered planet’s death-throes as quickly as possible -- a dangerous task in and of itself. From orbit, as their voidships are buffeted by the destruction, these ghoulish blast-waves are captured by immense, arcane wave-recorders. Later they are replicated back on Forge Worlds, where this energy is reborn in the form of Quake Shells. It is not uncommon for such shells to be named after the planets from which their potency has been captured. Quake Shells sometimes scream as they rocket through the air, and many suggest that this noise is in fact the combined death wails of a lost planet's population. The Tech-priests have not quashed these macabre rumours.
The weight of the Quake Shells depends upon on the power of the Exterminatus from which the energy was extracted. Though their mass is marginally less than those fired by a Stormsword's Hellhammer Cannon, they are fired over significantly larger distances. It is the extreme range of the cannon and its quake-effects on impact that makes it much admired by those Imperial commanders involved in siege warfare.
When one of these shells strikes its target, it does so with enormous, heart-stopping power, transferring the echoes of a planet-shattering blast into a localised area. When the smoke clears, if a smouldering hole has not appeared in the fortress walls, then the shell will have caused instant fissures; fault-lines will begin to appear across the perimeter of the citadel, meaning the next blow will be the one to enable the Imperial forces to breach its defences.
The recoil of the Quake Cannon is enormous, meaning that the Banesword's design is among the most robust of the vehicles in the Imperium. Being based on the STC of the Baneblade, only a handful of Forge Worlds are able to manufacture both the vehicle and the weapon. The Quake Cannon is also found mounted upon Imperial Titans such as the Warlord-class Battle Titans, where the engineering crew and Servitors maintain the weapon along with the utterances of the appropriate prayers. It was for these Titans that the weapons were initially designed and their Princepi utilised them in much the same way as the Baneswords which would later carry them -- blasting their way through fortress walls so that their God-Machines could march onward to victory.
On occasion, if no more suitable weapons are available, a skillful commander will be able to maneuver a vehicle to direct a Quake Cannon's fire towards large enemies. The reality that the Quake Cannon is hull-mounted and the Banesword is not a particularly swift vehicle means it is not especially suited to hunting daemonic war engines, monstrous alien lifeforms or Traitor Titans except at range.
Within the Banesword, arcane targeting Augurs are maintained by the Tech-priest Enginseers and their Servitors. Using this somewhat esoteric technology, the assiduous Enginseers monitor the blows of the Quake Cannon, often muttering prayers over the shoulders of the Banesword's driver or gunner. It is their skill that ensures, even over staggering distances, the accuracy of the weapon -- for a stray blast could have dire consequences. For instance, during the Cadian 87th's assault against Traitor Guardsmen on Chandrax II, a Quake Shell narrowly missed the top of a fortress wall and landed in the distance. The sudden vibrations disturbed a dormant Necron Monolith and the ensuing, implacable wave of awoken Necron Warriors ended up destroying the regiment.
- Warhammer 40,000 Munitorum - Quake Cannon (Digital Edition) pp. 84-89
- Warhammer 40,000 Munitorum Volume One, "Quake Cannon" (Digital Edition), pp. 110-113, 116-118