Historically this has been attributed to the workshop of Damián Forment (1532). Recent studies, however, indicate that the sculpture was worked on by Gabriel Joli, a Frenchman from the region of Picardy. It is a Renaissance sculpture made of polychrome alabaster. In the body of the altarpiece we can see the figures of Santiago, a pilgrim; Saint John the Baptist and Saint Michael. On the ledge is the Epiphany, the Descent and the Birth and in the attic, the Stations of the Cross, the 4 evangelists and two medallions with the prophet Isaiah and King David.
The chapel is decorated in the Plateresque style. On the floor of this area is the ossuary or common burial site, where the remains have been found of the people that were buried in the numbered tombs on the paved floor of the collegiate church.