Unidentified Aliens

A group of hostile, unnamed extraterrestrials who mount an assault on the Enterprise and operate at least one shuttlecraft. Data reports that they previously attacked the ship and then disappeared, their shuttle gone as well. Their taxonomy, motives, and long-term presence remain unknown; within the episode they function as a transient tactical threat whose sudden vanishing both heightens immediate suspense and leaves the crew with unresolved questions about origin and intent.