@inKraken My guess, is that like with the immortal cloud planet, the barriers surrounding the planets were too difficult to go through, so all the ships that tried to enter the atmosphere were basically annihilated. So the wreckage is surrounding the planets and scavengers loot the corpses. There isn't really an easy way to phrase that :S Based on what I'm reading/tried to understand from raws, the word "sky" was used, as in many "sky level", which is assumed to be heaven tier. So either A: sky meant earth tier, and devil of nine skies was a heaven tier, or B: There were actually a bunch of heaven tiers during the war that had the majority get wiped out to protect the human alliances. I am not sure either, but I would assume one of those two.
@AngleBoi7 You mean the battle form at the bottom of the holy lake from the one creep that had copper mouth? I'm pretty sure she got the whole of that, or so it looked like. Also, the title is "demon of the nine skies" is a heaven tier angel. So it isn't mixing sky and heaven, the title literally is "demon of the nine skies", or maybe it could be heavens? Dunno. Demon of the nine heavens sounds cooler to me lol xD But skies might be more accurate depending on the character translated :S