Wizkids Rules!

I have a question regarding how the disruptor cannon weapon upgrade from the Dominion Faction Pack works. The restrictions indicate that it can only be equipped to a Jem’hadar battleship and can only be fired from the rear firing arc. The problem is that neither battleship (the Faction Pack and expansion pack) have a rear firing arc. This upgrade seems unusable.

The ship in the Faction Pack does have a unique 45 degree center firing arc on the base. Is this center arc meant to be used for the disruptor cannon?

The icon displayed on the Disruptor Cannon card is for Secondary Firing Arc only. The term Secondary Firing Arc replaces the term Rear Firing Arc as seen in the original rulebook but still means the arc within the two dotted lines on the ship's base token.

In this specific case, as you've noted, the 45 degree center firing arc is the Secondary Firing Arc. As a result, this weapon can be fired only through that 45 degree center firing arc.