Here a contrast is made with the characteristics of heaven. John had been transported into heaven where he saw with his own eyes how light, bright, and white everything was, and by extension how much life (and hence song, joy, and pleasure) there was in the presence of God. But the abyss is characterized by dark, grey‑brown gloom, and by extension by depression, sorrow, and despondency. John now sees the dark and gloom of the abyss billowing over the earth. Given that the abyss is the home of the fallen angels, we are not surprised that what comes from this pit is dark and depressive—demonic.
2 He opened the shaft of the bottomless pit, and from the shaft rose smoke like the smoke of a great furnace, and the sun and the air were darkened with the smoke from the shaft.