The Maelstrom Mod introduces four new races to the Sins of a Solar Empire Rebellion Universe. They are independent of the original races and have unique strengths and weaknesses. Maelstrom is available for Rebellion, Diplomacy, Entrenchment and Original Sins.
Really adds many content which has real soul inside it. 3 races with their own unique flavour(not from a other universes maybe some insprations here and there). Totally recommending this mod to everyone.