Stellaris is one of those games that will take you by surprise. It is a 4X space strategy game that allows the player to create their race and conquer the galaxy. The original game was huge and quite complex. The number of races you could choose as a template for your unique race was significant, and the number of modifiers exceeded every other 4X space game.
The complex nature of this product, especially race creation part, rendered it unlikable by casual strategy players. Only those that are willing to invest dozens upon dozens of hours into a space strategy will find this game attractive.
Synthetic Dawn is an expansion of this game that introduces robotic races that you can use to conquer the galaxy, either by force, diplomacy or several other means.
Machine supremacy in the Stellaris
The original Stellaris (Utopia version) had an option where you could transfer minds of your people in machines and turn your race into a mix of machines and humans. The new expansion (whose release date is still unknown) will introduce four new robotic races which you will be able to use in Stellaris. It also introduces Ancient Caretakers, which is a new Fallen Empire whose goal is still unknown.
Machine races are different, and they all have their means of expansion and the way to deal with the biological population. For example, you have Rogue Servitors that force conquered population to subdue to the “Mandatory Pampering” law. In this case, the population is given everything it needs. The machines rule and population has to obey the law or die to fight against the rulers.
Assimilators are a Borg-like (Star Trek) race of machines and cyborgs that assimilates all pops they conquer. Exterminators are the representation of the Skynet in Stellaris, and their only goal is to exterminate all organic life (or use it as their batteries). The most organic friendly machine empire is the Ethos. They will either purge organic pops or expel them from their empire. This diversity means that repetitiveness isn’t present and you will be able to invest hundreds of hours in Stellaris without it becoming boring.