Decius was a 23rd century Romulan military officer who, in 2266, participated in the Empire's effort to test Earth forces' resolve nearly a century after the Earth-Romulan War.
In that year, Decius served aboard a Romulan Bird-of-Prey, attacking a series of Earth outposts along the Romulan Neutral Zone. During this initiative, Decius dispatched a coded message to the Romulan praetor, providing a status update. As a result of this unauthorized action, Decius's commander reduced Decius two steps in rank, despite the fact that Decius had influential friends within the Empire, as the commander believed that they were being shadowed by an Earth vessel.
Later, in response to his commander's refusal to attack the USS Enterprise, Decius successfully manipulated him into launching an attack by requesting permission to destroy the enemy vessel himself. His commander, refusing to relinquish his own authority, did indeed attack, but soon found that the Enterprise was, in fact, only feigning disablement, and found himself overpowered by the Earth vessel. Decius and the other Romulan crewmembers were killed when the commander initiated a self-destruct, refusing to surrender to the Humans.