Nightbringer | The Arthurian Online Encyclopedia

Holy Herb

And ... there by the way [King Bagdemagus] found a branch of an holy herb that was the sign of the Sangreal, and no knight found such tokens but he were a good liver.

Strangely, Bagdemagus is unlisted among knights who later achieve the Adventures of the Grail. Gawaine supposedly kills him sometime during the Quest, although the details are fuzzy.

Le Morte Darthur | Sir Thomas Malory, 1469-1470