en_tn/ezk/30/09.md

messengers will go out from before me in ships to terrorize a secure Cush

Messengers will bring the news of Egypt's destruction to Cush, who will be frightened by the news.

to terrorize a secure Cush

"in order to frighten Cush, who now feels safe from danger"

there will be anguish among them on the day of Egypt's doom

The abstract noun "anguish" and "doom" can be translated with the words "suffer" and "punish." AT: "the people of Cush will also suffer when I punish Egypt" (See: rc://en/ta/man/translate/figs-abstractnouns)

behold!

The word "behold" here adds emphasis to what follows. It can also be translated as "indeed!"

It is coming

"It" refers to the "great pain" or "great sorrow" that Cush will have when they are punished along with Egypt.