Rex

"We are the Shadow Garden. Or was it the Shadow Guardian? Oh, whatever. I’m Rex. Rex, the Game of Betrayal."

- Rex

Rex (レックス) was a Named Child of the Cult of Diablos, titled Game of Betrayal (叛逆遊戯). During the attack on Midgar Royal Spellsword Academy, he was tasked by Sir Gaunt to retrieve the Eye of Avarice artifact control unit from Sherry but was thwarted and killed by Shadow.

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

During the Cult'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 waist without wearing a mask.

Personality
"Difference in our strengths…… Do you really think you’re stronger than me?"

- Rex ferociously scowls at Glen

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.

Like many members of the Cult, Rex had quite a confident delusion that led him to completely convinced of his invincibility and have a severe overestimation of his own abilities.

Rex 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 student.

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.

Physical Prowess
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.

Magic
Rex was capable of using magic as he intensifying his kinetic vision to its limit and focusing his gaze, which he can detect any rapid movements. Even he able to channels all his magic into protecting his inside, including his heart.

In the anime, he was able to demonstrated a technique to create a net around himself that stretches using his magical power like a ball by linking both ends of his swords together to act as a barrier.

Battle Estimation Deduction
The reason Rex called himself the Game of Betrayal is because he can completely expose his victims with minimal information by solving the riddle that he grasped from his opponent into his mind and used it to his advantage.

Lutheran Barnett / Sir Gaunt
His superior. Their relationship was tense due to how little to no respect the two had for each other. The former Round Knight was patient with Rex's attitude until he reported what happen with the Eye of Avarice to which he was enraged and had threaten him to retrieve it from Sherry. When Rex didn't came back, the former Round Knight called him useless unaware that he was killed by Shadow.

Sherry Barnett
His target. Rex's cocky attitude became his undoing when he allowed the Researcher to escape where she late met up with Cid.

Glen
His opponent. Upon arriving to hunt down the Eye of Avarice from Sherry, Glen protected her from Rex's onslaught stating that his skills alone are enough to match against his magic abilities. Insulted, Rex was confident in killing the Knight and so he did with ease.

Marco Granger
One of his opponent offscreen, the Knight's incapacitated body was seen in the same room where Glen was killed.

Shadow
Although Rex was unable to identify the student as the Shadow Garden's leader, he was able to notice that he's too injured to keep fighting when he saw his blood stained uniform and thinks he used an artifact that boosts his abilities which he concluded that the student has no chances of defeating him. That is until Rex witnessed multiple corpses of his subordinates before being killed by Shadow before being complimented by him.