The Green Knight's tale is the tale of how Lyonesse became an ally to Amber. It went something like this…
Oberon wanted Lyonesse as an ally when he was founding Amber, but the Kings of Lyonesse were not convinced this was for the best. The kings were not in agreement. So, at the end of a Grand Conclave, they decided that the matter would be put in the hands of the gods - and settled in a martial tournament. Amber would send its Champion, and Lyonesse would issue hers. If Amber won, then Lyonesse would sign the treaties. If Lyonesse won, then it would remain a wholly independent land. Lyonesse's champion was the Green Knight.
Every year Amber would send a new champion, and every year Lyonesse would win. None could strike down the Green Knight in combat. Now, Oberon didn't care much for this approach and wanted the matter settled. He sent Dworkin and Osric to observe one of the bouts and they noted that the Green Knight was using a magic axe.
Osric offered up a new tournament and it was accepted. The rules were simple: if the Green Knight could behead Osric, the Green Knight won. If Osric beheaded the Green Knight, then Amber won. They would use Osric's axe. The Green Knight, seeing no way he could lose this, since Osric was letting him go first, accepted.
The Green Knight swung with all his might, but Osric's axe refused to harm the Prince. Osric swung his axe with half-strength, and slew the so-called immortal Green Knight. Blood wept from the axe blade, and the enchantment was believed destroyed.
Many claim that this is how Lyonesse came to be Amber's ally.
