There are several synonyms for the phrase "casts a shadow." Some alternatives include "creates a silhouette," "provokes a shade," "throws a gloom," "forms a dark outline," and "projects a penumbra." Depending on the context, these phrases can efficiently replace "casts a shadow" for a more specific description of the event. For instance, "creates a silhouette" is often used when referring to artistic or photographic endeavors where one desires a recognizable image while maintaining a sense of mystery or ambiguity. On the other hand, "forms a dark outline" may be useful in scientific or technical writing where precision and clarity are crucial.