Rex

Rex (レックス) was a Named Child of the Order of Diabolos, which is tasked to retrieve the Eye of Avarice artifact from Sherry.

Appearance
Rex had the appearance of a 'flippant man.' He had red hair with the eyes of a 'starving feral dog.'

During the Order's siege on Midgar Academy, he wore an imitation of the Shadow Garden uniform which included a jet-black coat and a mask.

In the anime, Rex is seen in a black uniform with a red vest, black boots, and carries two large swords on his back without wearing a mask.

Personality
Rex is a vicious, arrogant and capricious man who sees and everything just to play. He likes to humiliate those who he believes are below him, but he can be good at provoking his opponents in order to take advantage of their exposed points and weaknesses to do so. He never felt fear until he sweated in terror for the first time in his life, when he saw all of his men being eliminated by a single students.

Midgar Academy Terrorist Attack
Rex arrived at Midgar Kingdom and joined Lutheran Barnett to commit misdeeds throughout the capital, while claiming to be from the Shadow Garden, with their purpose to lure them out. When he heard the lost contact report of his men, he ask his superiors what's the next step, which he replied that its fine because he located the item he need which is their priority to retrieving the item.

Rex and the cult forces under Lutheran infiltrate and took over the Midgar Academy. While his fellow Children rounded up the students and killed anyone that opposed them, Rex headed to Sherry Barnett's study room and retrieved the Eye of Avarice's control unit. He encountered Sherry and was about to kill her only for two Crimson Order knights to intervene. Sherry escaped, while Rex defeated the knights.

Rex met up with Lutheran and informed him of what transpired, then he become angry until he threatened Rex because for his playing around. Before Rex and his men immediately went out to search for the artifact, he informed that several of his men have been killed which Lutheran suggest that Shadow Garden have come until Rex tells the Ex-Rounds to be careful. While walking through the school's premise, he watched as his men are being taken out by a student much to Rex's shock.

Rex fought back against the interloper only to be overwhelmed by his incredible power. Rex deduced that the student might be using an artifact and having noticed wounds on the boy, also believed that he might be reaching his limit. He taunted the student in hopes to get him to act. When it worked, Rex prepared himself only to be launched away and crashed into a classroom.

Rex laughed, thinking he had won only to look around and find the corpses of multiple Children. Upon realizing that all these Children were in fact killed by that student, Rex sweated in terror for the first time in his life. He only had a brief moment to muse about that boy's unlimited strength before said boy entered the room and eviscerated him.

Powers & Abilities
Rex was the most powerful warriors as an Named Child, considering "First Children" who have provided extraordinary contributions to the Cult. Rex possessed stronger physical strength and magical powers compared to the average knight, from which the cult granted him a name, also mentally stable.

Rex was an excellent magic swordsman being able to best both magicless Glen and Marco Granger in a fight. However, he (like everyone else in the Cult) were too weak against Shadow and the Shadow Garden.

In the anime, he was able to create a magic net around him like a ball by linking both ends of his swords together to act as a barrier.