There are several examples of figurative language in the story, including similes. Figurative language allows the reader to better imagine the things that are described.
[A simile is] a figure of speech in which two things, essentially different but thought to be alike in one or more respects, are compared using “like,” “as,” “as if,” or “such” for the purpose of explanation, allusion, or ornament. (enotes guide to literary terms)
There are many types of figurative language in the story. For example, the dark sky is described as being “like moist black velvet” and trying to see through it is “like trying to see through a blanket.” These similes help the reader to picture the darkness, and creates an image in the reader’s mind.
Another example of figurative language is in the general’s giddy description of how he traps ships in the island.
The general chuckled. "They indicate a channel," he said, "where there's none; giant rocks with razor edges crouch like a sea monster with wide-open jaws. They can crush a ship as easily as I crush this nut."
The comparison of the rocks to a sea monster and the crushing of the ships to crushing a nut really gives the reader the creeps. The choice of figurative language aids in guiding the reader to a specific mood. We feel creeped out by the creepy images. It creates suspense because it foreshadows disaster. We know that something bad will happen.