Revenant is an enemy from Final Fantasy IV: The After Years.
As in the original, Revenants are highly resistant to statuses, but are extremely weak to Fire and Holy-elemental attacks. A casting of Fira is more than enough to dispose of one in one shot, while two castings of a group-Fira will more than likely wipe out a group of Revenants. Overall, they are not difficult enemies to defeat.
Revenants are animated corpses or ghosts in Western folklore that are said to return from the dead to terrorize the living. The word "revenant" is French (Fr. revenir, "to return") and means "one who returns".