Some translations set poetry farther to the right than the rest of the text to show that it is poetry. The ULB does this with the poetry in 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]])