In the present context “fire” describes the (destroying) anger of God (Hosea 8:5; Nahum 1:6; Isaiah 66:15–16; Jeremiah 15:14; Ezekiel 21:31). So it climaxes the earlier reference to fire in Revelation 9:1–21. The addition of the word “lake” underscores the size of the fire, that is, the intensity and the reach of God’s anger. It is far greater than simply a furnace (Daniel 3:6, Daniel 3:19). This is a picture of hell.
10 and the devil who had deceived them was thrown into the lake of fire and sulfur where the beast and the false prophet were, and they will be tormented day and night forever and ever.