Animus wrote:Nothing suggests that the Chaos Gods are confined to the galaxy, indeed they're said to be not even universal but multiversal.
I've never read that. Do you have a source? Everything I've read would indicate that the Chaos Gods are powered by and tied to mortal emotions. Without mortals, you get no Gods. That was sort of the whole point of the Horus Heresy. Had humanity "won", they would have burned bright, but short and taken the Gods with them when they went extinct. Instead, humanity survives in a sad state, but in a state that nourishes the Gods indefinitely.