How does magic and the fantastic work in this poem? Is magic presented in opposition to Christianity?

Despite its Christian message, the poem has strong roots in Celtic pagan myth. There are many elements common to pre-Christian Celtic mythology, such as the waiting period of twelve months and a day, the Beheading Game, and the Temptation Game. The Green Knight himself is a strongly pagan character, similar to the Green Man or Wild Man of the Woods who symbolizes fertility in folklore. Gawain's journey can even be seen as the hero's archetypical encounter with the Otherworld, an essential theme in pagan belief. The Pentangle is often a pagan symbol; thus Gawain' s shield, with the Pentangle on one side and the Virgin Mary on the other, comes to represent the dual pagan/Christian nature of the poem.