Colin (original surname unknown, later dubbed MacLeod) was a Scottish barbarian who lead his own clan against the Roman invasion of Britain, lead by General Marcus Octavius in 125 CE, with a force of merely 400 against the 2000 Roman's, defeat seemed inevitable, but Colin wished to fight for the sake of his honor. Fearing for her husband, Colin's wife, Moya, drugged him and attempted to convince Marcus to retreat, in exchange for a night with her.
When Marcus callously refused her offer, she attempted to kill him with a hidden blade. To her shock, Octvaius survived and took her prisoner. Octvaius sadistically had Moya crucified on a cliff overlooking the massacre of her clan.
Colin awoke in the morning and found his clan dead. Moya made him swear not to take revenge before dying. Enraged, Colin attempted to infiltrate the Roman camp to assassinate Marcus. As he approached Marcus' tent, he and Marcus experienced the buzz, which paralysed Colin. Aware of Colin's immortality, Marcus challenged Colin to a duel on horseback. Demonstrating his skill, Marcus split Colin's sword, and head, open with a single blow, and followed his fleeing horse to ensure a beheading. Miraculously, Colin's dead body fell off his horse at Stonehenge and Marcus was forced to abandon his prize, due to the rules of the Game preventing combat on holy ground. Over several months, during which the Romans eventually retreated from Britain, Colin's body slowly healed and eventually he awoke. He was greeted by a druidic spirit named Amergan, who explained his nature and the Game, serving as a mentor and source of irritation for the rest of Colin's life. Despite the wonder of his immortality, Colin never gave up on his hatred of Marcus and devoted his life to revenge. In 476 CE, Colin led an army of barbarians to sack Rome itself. He confronts the now-Emperor Marcus Octvaius and boasted at his victory. Marcus, completely unfazed, calmly stated that he would rebuild the glory of Rome again until he has created his prefect world. Spitting at Marcus' dream, Colin attacked, only for Marcus to defeat him with elegant and brutal ease. Ready to behead Colin, Marcus was forced to retreat when barbarian forces attacked. Colin continued to be a thorn in Marcus' side for centuries, forever working to undo Marcus' attempts at a perfect civilization. Colin constantly hounded Marcus across the Middle East and hunting him in China in 763 CE
In the 11th century, Colin joined the MacLeod clan in Scotland, to aid them in a battle against the British army, which Marcus lead. Overwhelmed and "killed" in battle, he was buried a hero and granted the name Colin MacLeod. Despite the peace he found in the clan, and the love he had developed with a woman named Deborah, Colin refused to remain. Waiting until he was buried, he attempted to flee unnoticed only for the clan to hunt him down. Ready to kill him despite Deborah's protests, Colin was saved by the clan leader, Gregor, who asked him to remember his new name and live with honor, something Colin had abandoned in his hunt for Marcus. Colin would fight Marcus again in Japan during the 16th century. Once again leading an opposing force against Marcus' rule, Colin confronted him in a burning building, where they dueled. Once again, Colin's sword broke under Marcus' strength and Colin grab a nearby one that was much stronger, until burning rubble separated the two and Marcus fled. Colin would keep his new sword for the rest of his life. Colin's vengeance brought him to fight against Marcus again and again. He fought as a sailor at Trafalgar during the 19th century, as a soldier in World War 1, and as a fighter pilot in World War 2.
During WWII, on a mission, Colin, fighting with the Royal Air Force, again attacked Marcus, now a member of the SS, and the two fought on the wing of Marcus' plane until a damaged engine destroyed the plane. The two fell to the ground and awoke in the church they had fallen into, and Marcus, noticing they were on holy ground, gave a weakened and helpless Colin his sword back. Taking a moment, Marcus admonished Colin for wasting his immortality chasing him, advising him to move on and find a new reason to live as Marcus had after Rome's destruction. Colin stubbornly refused, and Marcus left disappointed.
What happened between the incident at the church and the Gathering in 2187 is not known. In the year 2187, Colin followed Marcus to the United States. He fought and killed Malike, whose death and Quickening were witnessed by Marcus and his concubine, Kyala, who Marcus rescued and fell for in Japan. Colin then traveled to New York, where he found the city a wasteland, dominated by a giant gold building - a cross between a skyscraper and a castle. Narrowly escaping Marcus' soldiers, Colin escaped to a bar, where he met Dahlia, who reminded him of his lost loves, Moya and Deborah. He was particularly reminded of Moya when Dahlia, a prostitute, said "You don't need that. All you need is me", because Colin was drinking whiskey when they met; the memory he had was of a time before battle with Marcus and his Legion, when Moya said the same thing when Colin was drinking.
Note: Colin's original surname is not MacLeod, he is dubbed MacLeod by the clan after joining them and dying in battle.