Theîon (θεῖον) means brimstone or sulfur — the burning mineral of divine judgment. The word shares its root with theos (God), reflecting the ancient view that burning sulfur was 'divine fire.'
Brimstone in Scripture consistently signals divine wrath. Sodom and Gomorrah established the archetype (Genesis 19:24). Revelation amplifies it: the lake of fire burns with theion — final destination for Satan, the beast, and all whose names are absent from the Book of Life (Revelation 19:20; 20:10; 21:8). A God who tolerates evil forever is not holy. The lake of fire expresses that God takes sin seriously. The good news: Christ drank the cup of wrath so believers need not.