Marcus Constantine was born in Rome in 441 BC. He grew up in one of the biggest empires in world history, and became a soldier for the Roman army, eventually rising to the rank of general.

He experienced his First Death during the Sack of Rome when he was killed by Gauls in 390 BC. He then revived as an Immortal, and met Flavius Sulla, who taught him all about being Immortal. The teachings he acquired with Sulla were eventually transmitted to his first pupil, Marconus. Even as an Immortal, Constantine remained a Roman general for generations.

In the year AD 60, as a general in Britannia, he found a young Celt named Ceirdwyn, to whom he taught the rules of the Immortals. He left the military for her, and settled with her in Rome. They were very fond of each other, but Ceirdwyn decided to leave him in the year AD 73.