The phrase "by night" is commonly used to indicate actions or events that occur during the night. However, there are several alternative phrases that can be used to convey the same meaning, such as "at night," "during the nighttime," "in the dark hours," "when the sun goes down," and "after dusk." These synonyms can be useful when trying to add variety to your writing or when searching for a more concise way to express the same idea. Keep in mind that the context of the sentence and the tone of the piece can also influence the choice of phrasing.