According to Cailleux, Ismarus was the legendary town of Ys, which was situated in the extreme west of Brittany, near Douarnenez. After
the town was engulfed by the sea, the French sang,
‘Since Ys is no more, Paris is without rival’.
In this town, the high priest, Hu, was said to be the custodian of the Holy Grail, the legendary chalice known from the writings of Chrétien de Troyes, among others. In Homer’s time, the high priest was called Maro, as Odysseus recounts:
"... With me I had a goat-skin of the dark, sweet wine, which Maro, son of Euanthes, had given me, the priest of Apollo, the god who used to watch over Ismarus. And he had given it me because we had protected him with his child and wife out of reverence; for he dwelt in a wooded grove of Phoebus Apollo. And he gave me splendid gifts: of well-wrought gold he gave me seven talents, and he gave me a mixing-bow/l all of silver; and besides these, wine, wherewith he filled twelve jars in all, wine sweet and unmixed, a drink divine. .. . (Od. IX, 196-205)"