The Eighteenth or XVIII, is one of Rome's elite Legions in Ryse: Son of Rome.
During the battle, the Eighteenth is tasked solely with defending the district around the Emperor Nero's palace, and as a result most of the legion is still fresh and combat effective late in the battle as the barbarians only now reach the palace in force. After general Marius Titus arrives to reinforce the Eighteenth, the legion begins fending off a massive barbarian assault as the invaders swarm the defenses. Just as the defense is about to break, Marius orders a catapult nest to fire directly on top of their position in the now completely overrun palace courtyard. This bold move shatters the barbarian charge and the attackers withdraw. Soon after this, the barbarian horde learns of Boudica's demise as Centurion Severus displays her severed head, and the invaders abandon the battle, leaving the Eighteenth as the deciding force who turned back the enemy and saved Rome from total destruction.
- When Marius organizes the palace defenders, the Eighteenth's standard (battle flag) bares the numerals of the Fourteenth Legion, as do the helmets of all the soldiers.