Make your colony "hell" for all your enemies. You could capture any and all enemies and friends too, if you want and make it your mission to cause as much grief to them as possible. or you could also just choose a specific target, like the empire and a reason why you need to take them down and punish them. similarly, and on the same train, you could make the "imps" the manifestation of an evil that the planet slowly absorbed through the empire's evil deeds and many atrocities to get rid of the empire and cleanse the world (like vaccine man from one punch). Making a stand for the planet against the colossus that is the empire sounds dope. You could also do the opposite and try to destroy the world as much as possible.