Warhammer 40,000

The 41st Millenia was a time of strife and trouble, of apostasy and heresy in an uncaring galaxy wide war of the fittest. Ranging from the oldest races such as the Necrons, Aeldari, Drukhari, Greenskins, to the youngest such as the T'au empire.

The Forces of Chaos under the command of the Despoiler, everso lusting, cause as much havoc as they could in the lands of the Imperium who answers their hubris with their own through the numberless body count of the Imperium Guard, the great surfing cathedrals of the Imperial Navy, the pious stalwart determination of the Adepta Sororitas, or through the sheer will of the Astartes.

Then there are the Tyranids, a Hivemind than a faction, and an all-devouring terror that adapts and overcomes whatever is thrown at them no matter what. If they require sabotage from within, they will send their cults called Genestealers which will infect and breed before rising from the deepest pits and sewers of a world, unleashing havoc to all of its inhabitants and much importantly, the Planetary Defense which should falter in order for the Star Children to take over.

There are many other forces at play, sub-factions within the major players. What happens in this malevolent galaxy that you have chosen is all up to you.