Some translations set each line of poetry farther to the right than the rest of the text to make it easier to read. The ULB does this with verses 15 and 17-18.
Scholars have suggested many different ideas about these two witnesses. Translators do not need to understand this passage to accurately translate it. (See: [[rc://en/tw/dict/bible/kt/prophet]])
This image is seen several times in the Book of Revelation. It is a picture of hell as being inescapable and the opposite direction as heaven. (See: [[rc://en/tw/dict/bible/kt/hell]])