How to explain christian elements in Sir Gawain and the Green Knight?

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......Biblical parallels can be found in the appearance of Bertilak's castle (Paradise) and the role of his wife as temptress (Eve). Accordingly, Gawain loses his moral innocence when his value system is shattered by the end of the poem. Such an allegory emphasizes once more the poet's Christian message, and the relationship between mankind and the divine.

In contrast to the questionable nature of the chivalric code, the poet upholds Christian faith as the ultimate, saving grace for humanity. Ever pious, Gawain continuously finds guidance in God: from the image of the Virgin Mary on the inside of his shield to his prayers while journeying alone, to his narrow escape from the adulterous temptations of Lady Bertilak. It is, in a sense, faith in God which enables mankind to negotiate between the dangers of human society and the dangers of the natural world. To affirm this, the poem concludes with a supplication to Jesus Christ, the Savior.