The Dominion is a militaristic, imperialist[1]human faction and ancient enemy of the Freelancers, as well as the primary enemy in Anthem. Philosophically opposed to the Freelancers, the Dominion desires to subjugate all of humanity under their rule.[2] To that end, the Dominion aims to control the instruments of the Shapers[2] and harness the power of the Anthem of Creation.[3]
The questline where you will most often fight the Dominion would be for the Arcanists loyalty with Matthias.