1: θεῖον
(Strong's #2303 — Noun Neuter — theion — thi'-on )

originally denoted "fire from heaven." It is connected with sulphur. Places touched by lightning were called theia, and, as lightning leaves a sulphurous smell, and sulphur was used in pagan purifications, it received the name of theion, Luke 17:29; Revelation 9:17,18; 14:10; 19:20; 20:10; 21:8 .

2: θειώδης
(Strong's #2306 — Adjective — theiodes — thi-o'-dace )

akin to No. 1, signifies "brimstone-like, or consisting of brimstone," Revelation 9:17 .