White Stag

Chrétien de Troyes tells us of the custom of hunting the white stag, and how whoever can kill it must kiss the fairest maid in the court. This custom seems already to have fallen into disuse, for Arthur wishes to revive it, despite Gawaine's prudent advice that choosing the fairest maid can only cause trouble, since every knight thinks his lady the fairest.

By "maiden", I think we must understand virgin or at least unmarried woman, since nobody ever thinks of solving the problem by naming the Queen (Guenevere) as fairest.

D.D.R. Owen, in the notes to his translation of Chrétien, identifies the White Stag as otherwordly in origin. It may have gotten into Malory as the white hart whose appearance with a white brachet and sixty black hounds marked Nimue's coming to court.