In the future humanity is visited by a Stanisław Lem alien that uplifted the species to its high water mark. Everything is pretty cool, stuff that seems like magic was everyday reality, long live Leto II, blah blah blah.
Unfortunately a Lovecraftian horror was also out there in the universe and it didn't seem to care much for that alien. It showed up in Sol System and brought about an end to the high water mark of the species.
The stories say that the two fought and in the final battle the alien banished the horror at the cost of its own consciousness. That was a long time ago and frankly you should be skeptical of the events described. Humans don't even know why they built sentient robots in their own image anymore, let alone the history of beings that defy our limited intelligence.
Whatever actually happened, humanity and its sibling species (the aforementioned robots and predominantly space dwelling abhumans) live a fragile existence from pockets of minor security in a universe that they understand very little of. One of those pockets is a city that lies in the shadow of the alien, now humanity's sleeping god. Its military is the resurrected dead, chosen by automata that answer to the god no one can hear.
Sounds like shit's pretty fucked, why bother with a standing army when you don't know why your talking tractor is a sentient being, right? Turns out that this wasn't the first time the alien and the horror played a little rough with their ant farms. The ants from those farms are here too, each following after the dynamic duo. They all have their own agendas, unfortunately exterminating the natives is the common thread between them. It turns out that gods are beheld in different ways by different beings.