Heyo. I had an idea that would allow us to use both ideas. We can have both the negative creations that Jays suggested and the half formed beings that Gauge suggested. We could have the negative creation come first at the beginning o the the galaxy, with the half formed beings created after over a period of time.
The Mirror of course would be the negative dimensions that the negative creation beings originate from, with the half formed beings sorta shoved into there by the Council when they make trouble.
Also a few people suggested that we dont call these beings "demons" as they are from another galaxy. Thoth suggested the name Mirrai.
Please give your opinion on these ideas.