The Green Knight is the mysterious immortal guardian of the sacred places of Bretonnia, a spectral warrior clad in ancient green armour who appears without warning to challenge those who would test their worth. Neither wholly living nor dead, he is said to be an emissary of the Lady of the Lake, bound to defend her shrines, barrows, and holy sites against desecration.
Knights questing for the Grail must often face the Green Knight in single combat, for he bars the way to the Lady's blessing. To defeat or endure him is to prove oneself worthy; to fail is to be found wanting. He fights with supernatural skill and cannot be permanently slain, vanishing in a swirl of leaves only to return whenever the realm has need of him.
Legend holds that the Green Knight is in truth Gilles le Breton, the Uniter and first king, granted immortality by the Lady so that he might rise again in Bretonnia's darkest hour. His appearance in battle is taken as an omen of both peril and hope.