The universe is cracking at the seams. External threats have revealed all the problems between people. Humanity has grown too confident in its own immortality. And has gotten far too relaxed.
For which it was punished. Now the whole Habitable Cosmos is waiting for difficult times. Problems have to be solved somehow.
Well, me and my team are famous "problem-solvers," whatever you call it. So, dear Xenos, it’s your own fault!
As they say: “Whoever comes to us with a sword will get a BFG charge to the head!”
For the Emperor! Or is that from another book?