This decorative initial capital letter “M” is made from the crucified Jesus, complete with a face at his feet probably meant to be a skull representing Golgatha, the name of the skull-shaped hill where the crucifixion happened, and a person on either side of the crucified Christ: probably they are the disciple whom Jesus loved, and Mary the mother of Jesus, who by this time was no longer the Virgin Mary since she had given birth to James, the younger brother of Jesus.
This would be a good letter to use on an Easter card!