"Complete darkness" here is a metaphor for destruction. Alternate translation: "Destruction is reserved for his treasures" or "His treasures will be destroyed" (See: [[rc://en/ta/man/translate/figs-metaphor]])
Here "devour" is a metaphor meaning destroy. Alternate translation: "a fire that is not fanned will destroy him" (See: [[rc://en/ta/man/translate/figs-metaphor]])
The phrase "not fanned" implies that no human will start the fire. Rather, God will cause the fire. Alternate translation: "a fire that is not started by humans will destroy him" or "God will cause a fire to destroy him" (See: [[rc://en/ta/man/translate/figs-explicit]])