Callistus was born a slave and his master entrusted a large sum to him to open a bank. The bank opened, took in deposits and made some loans to people who refused to pay them back, The bank went bust. Knowing he would be punished, Callistus fled, but was caught and returned to his owner. Callistus was sentenced to work the tin mines. By a quirk of Roman law, the ownership of Callistus was transferred to the state and he was later ransomed out of his sentence, becoming a free man. He was martyred.