Evelyn's Emergency Backup Plan

Evelyn's Emergency Backup Plan is a single-shot spell cannon. It has a large fore-section which narrows to a pair of gemstone prongs. Behind that is a shield projector, and a pair of gold and mithral laced handles. At the rear is a bracket designed to hold something large and spherical - the ammunition.
The ammo is a twenty-five-centimeter, flawless artificial ruby that Evelyn has spent almost four years charging. It contains roughly one thousand, six hundred times the mana she possesses at full capacity.
The entire front section of the weapon is designed to be disposable and burn out after a single shot.
Evelyn describes the weapon as being her failsafe, "for when something absolutely needs to die".