Apocalypse Gun

Apocalypse Gun [Mount]

This massive three-barreled cannon weighs your mount down tremendously, but the damage it deals makes structural problems a minor concern.
Benefit: Once every seven [Rounds] as a standard action while riding your mount, you may create a 100 ft radius spread originating from target creature within [Extreme] range that moves with that creature and lasts three [Rounds]. Once per [Round] on your turn, without spending an action, you may deal 15d6 damage to all creatures within the spread. A successful Reflex save (DC 10 + 1/2 your level + your KOM) halves the damage.