There are many synonyms for the phrase "evil star." One of the most common is "bad omen," which suggests that the star is a sign of something negative to come. Another synonym is "misfortune," which implies that the star is a harbinger of bad luck or trouble. Some people might also use "devil's star" or "demon star" to describe a particularly malevolent celestial body. In general, any negative or ominous term could be used as a synonym for "evil star," depending on the speaker's intentions and beliefs about the star's nature and significance.