John Proudstar was a mutant human from 20th century Earth. He became a member of the X-Men shortly before his death. A time traveling team of X-Men and personnel from the USS Enterprise-E found a version of Proudstar working aboard the USS Saratoga as a Starfleet lieutenant during the Battle of Wolf 359. Proudstar sacrificed himself by jumping in the way of Borg weapons fire in order to save the life of Benjamin Sisko. Sisko mourned the loss of this officer. (TNG comic: "Second Contact")