Father Chadwick Vita was a monk who presided over the church of a small English village. One day he came across a mysterious entity with healing powers. He thought it an angel. He took the "angel" to his church and cared for it, developing a quasi-paternal attitude towards it.
Father Vita would take the ill to the "angel" to be healed. When it sensed that its enemy had come close to finding it, he comforted it and reassured it that nobody was after it. He urged it to soldier on and fulfil its God-given mission to help others.
During an apparent outbreak of the Black Death, Chadwick met the Tenth Doctor, who sought the faith healer he had heard about. The Doctor left after being shown the "angel" doing its work with the sick. He soon returned, chased by three Macro-viruses which Father Vita mistook for demons. Realising these "demons" were the enemies he was warned about, he tried to get to the "angel" before they did, but was attacked. As soon as the healer regained his full powers, Father Chadwick was the first one to be saved and healed. He asked the healer to stay, but it left to win its war against the viruses on its home planet. (COMIC: Black Death White Life)