My favorite elements of this were the evaporation and the last moments. Somehow starting with the city evaporating and ending with the world evaporating is a really good use of repetition. You have the same thing, but suddenly scaled up massively. It feels like nuclear holocaust to me. Because of the mention of last moments, I feel I urgently need to understand the situation, even though it seems hopeless. I am a bit confused about the relationship between the behemoth and the mountains and sky, probably because it is a lot for 30 words. I think it is cool if they represent earth/heaven - life/afterlife, but I can’t quite tell if they are threatening the protagonist or aiding him. What is the nature of the struggle? I think it would be a good way to start a story!