This is a great site that explains very well Gawain's Penance ~ reading this will definitely help you understand the Five of Swords in this deck. http://www.timelessmyths.com/arthurian/greenknight.html
"Gawain and his horse return to the court carrying evident of his misdeeds." ~ Anne-Marie Ferguson
The picture of this card shows a desolate place yet there is the promise of growth(the sun is shining though in a kind of fog). We see Gawain's horse with what looks like a woman unconscious, thrown over it, riding through a pond filled with lush purple and green flowers.
If you know the story of Gawain's Penance, he reluctantly welcomed the Green Knight's challenge game of 'beheading'.
Gawain road his horse and was welcomed at a castle near the Green Knight's, owned by Lord Bertilak de Hautdesert and his beautiful wife. Bertilak offered the Gawain lodging, since the Green Chapel was not far away.
Bertilak told his guest that he would be going on a hunting trip, his wife would entertain the guest during the day. Bertilak told Gawain that they should exchange gifts each day the host returned from hunting. Bertilak would give the hero the gift from his hunt, while Gawain would give to his host anything that the hero would win in his castle.
The first 2 nights Bertilak's wife tried to lure Gawain to her bed, which he gentle refused. She in turn gave Gawain a kiss. Bertilak returning from the hunt gave Gawain what he had killed and Gawain in turn gave Bertilak a kiss.
But the 3rd night, instead of a kiss Bertilak's wife gave Gawain her silk Green Girdle which he was thrilled as it protects whoever has it from harm. When Bertilak returned from the hunt and gave Gawain the fox that was killed, Gawain did not give Bertilak the silk Green Girdle, instead he only gave a kiss. After this, Gawain prepared battle with the Green Knight not knowing Bertilak 'was' the Green Knight.
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Looking up Fox Medicine, in detriment it warns us not to use our cleverness dishonestly. Gawain had quite cunningly, like a fox, hid the girdle from Bertilak to save his neck from the Green Knight. Fox' need to stay hidden in order to survive. And Gawain wanted to protect himself and so wasn't open to Bertilak about the girdle.
In a positive sense, the 5 of swords is about being ready to protect and defend ourselves so we can stay true to our inner purpose/vision. But Gawain hid the Girdle for his own ego pride, creating the shadow side of the fox energy. When the Green Knight spared Gawain (with only a nick on his neck) he showed his true self as Lord Bertilak and Gawain felt 'shamed' for keeping the Girdle as protection.
The Green Knight was not the tyrant he was made out to believe, he showed us we don't need to win or fear being defeated if we speak and communicate what truly comes from our inner heart.
Gawain realized he still had a lot to learn to overcome before becoming a Knight of Pure Heart. His ego deflated, he realized his conflict was an inner one and he had allowed the Green Knight's challenge to affect his emotions. If he had been honest and truthful to Lord Bertilake, he would have won this test/challenge with a richer understanding instead of feeling 'defeated' inwardly.