The challenge in designing a polyhedral sundial such as this one is to set a separate dial on each face of the shape, so that as many as are receiving the sun tell the time. In this case the shape is based on an octagon and there are dials on nine faces - the two large octagonal sides, and seven of the connecting rectangles (the bottom rectangle is supported by the base).
It was made by the German mathematician Nicolaus Kratzer, who came to England in about 1518 and was astronomer to King Henry VIII. He made this instrument Cardinal Wolsey, Henry VIII’s chief adviser; the four-sided base has Wolsey's arms, the arms of York Minster, and (on two sides) a cardinal's hat.
Cardinal Wolsey studied theology at Magdalen College, Oxford and also taught at the University, as well as founding Christ Church in 1524. He was Henry VIII’s closest aide until he failed to get the King’s first marriage annulled when he was stripped of his land and title.