Dark flare is a phrase that might refer to an intense, sudden burst of darkness or an ominous mood. If you want to convey a similar meaning while avoiding repetition, you could use synonyms such as "blackout," "eclipse," "shadow burst," or "gloom eruption." Alternatively, if you're talking about a more specific type of phenomenon, you might opt for terms like "umbral outburst," "abyssal surge," or "nighttime explosion." Whatever word or phrase you choose, it's important to balance your desired connotation with the surrounding language, so as to paint a clear picture and evoke the desired emotional response from your reader or listener.