Sergeant Rex Power Colt is the protagonist of Far Cry 3: Blood Dragon, a satirical homage to the sci-fi and action movies of the 1980s. Naturally, he's got a gleaming chrome robotic left arm and a glowing Cyber-Eye to match it, owing to his status as a Mark IV Cyber-Commando. He is voiced by iconic 80's movie actor Michael Biehn.
Rex was originally a normal soldier, fighting for the U.S. Military alongside his partner and best friend, Lieutenant T. T. "Spider" Brown. During this period, Rex and Spider fought together all over the world, including an op in the irradiated ruins of Quebec, Canada, where the two of them rescued Dr. Elizabeth Veronica Darling and her team of scientists, who were being held hostage by an unknown group. Eventually, when serving in Vietnam War II, both Rex and Spider were killed in action, at which point their bodies were surgically repaired and technologically upgraded, and both soldiers were reanimated as Mark I Cyber-Commandos. After this, both men served in the special ops unit known as Omega Force, under the command of the esteemed Cyber-Commando,Colonel Ike Sloan.
Although Rex possesses increased durability and superhuman strength and agility as a result of his cyber-enhancements, the reanimation procedure damaged the memory centers of his brain, and Rex's memories of his original life before he died and became a Cyber-Commando are spotty at best. He has mentioned that he can remember his parents and some of his life growing up, and also remembers parts of Vietnam War II, but other parts of his life are gone completely, such as the mission where he and Spider rescued Dr. Darling.
Rex's upgrades were designed to serve him as a flexible combat specialist, and he has advanced training, both real and downloaded, with a wide variety of weaponry and vehicles. His frame is reinforced against bullets, though he can still benefit from wearing body armour, and he has significantly superhuman strength, allowing him to carry a Terror 4000 minigun around in his inventory like a regular weapon. Specific benefits include a metal-reinforced skeleton, so that he can fall any distance without being injured, a built-in rebreather, allowing him to remain underwater indefinitely without surfacing for air, and his signature Cyber-Eye, which has a built-in zoom functionality and allows him to tag enemies and animals from a significant distance away, letting him track their position even through walls and terrain.
As he continued working for Omega Force, Rex was gradually upgraded until he qualified as a Mark IV Cyber-Commando, the best of the best, but it seems he and Spider eventually left Omega Force for unknown reasons. In 2007, Rex and Spider are deployed into a remote island chain that has been taken over by forces hostile to the United States, only to discover their enemy is Omega Force, with Sloan having gone rogue after upgrading himself and his soldiers into Mark V Cyber-Commandos. Soon, Rex is alone on the island, guided by the voice of Dr. Darling, and the two of them must work together to stop Sloan's evil plans, take the island back from Omega Force, and save the Human race in the name of American freedom!