A descendant of the original crew who serves as an officer aboard the alternate, century-old Enterprise and carries out Captain Lorian's orders, including his raid on the original ship.
Greer appears in the Enterprise episode E². He is one of the later generations born aboard the Enterprise that was thrown back to 2037 and spent more than a century waiting to help its younger self.
Greer serves on the bridge under Lorian. When the two crews disagree about how to get Jonathan Archer's ship through the Kovaalan corridor, Lorian decides to take the plasma injectors he needs by force, and Greer joins the boarding party that seizes them.
He is uneasy about attacking people who are, in effect, his own ancestors. After Archer and Lorian are reconciled, Greer is among the crew who fight a rearguard action so that the younger Enterprise can reach its rendezvous.