Complex sentence: Starships begin to enter the wormhole to explore, colonize and trade, their crews unaware that they are entering a region of space controlled by the Dominion, a union of planets ordered by force and intimidation.
Split into simpler sentences: Starships begin to enter the wormhole to explore, colonize and trade. The crews on the ships were unaware that they are entering a region of space controlled by the Dominion, a union of planets ordered by force and intimidation.