The phrase "a vision of the night" is the same thing as "a dream." The two phrases emphasize that soon it will be like the invading army was never there. (See: [[rc://en/ta/man/translate/figs-doublet]] and [[rc://en/ta/man/translate/figs-simile]])
The name "Ariel" is another name for Jerusalem, and it represents the people who live there. See how you translated "Ariel" in [Isaiah 29:1](./01.md). Alternate translation: "fight against the people of Ariel" (See: [[rc://en/ta/man/translate/figs-metonymy]])
The word "her" refers to Ariel which represents the people who live there. Alternate translation: "their stronghold. They will attack the city of Ariel and its defenses and cause the people to be in great distress" (See: [[rc://en/ta/man/translate/figs-metonymy]])
These similes mean that the enemy will expect victory but they will fail because God will not allow them to conquer Jerusalem. (See: [[rc://en/ta/man/translate/figs-simile]])