In the Christian tradition, holy cards or prayer cards are small, devotional pictures for the use of the faithful that usually depict a religious scene or a saint in an image about the size of a playing card. The reverse typically contains a prayer, some of which promise an indulgence for its recitation.

Saint Christopher is venerated by several Christian denominations as a martyr killed in the reign of the 3rd-century Roman emperor Decius, or alternatively under the emperor Maximinus Daia. There appears to be confusion due to the similarity in names "Decius" and "Daia". Churches and monasteries were named after him by the 7th century.