These Mortals — Margaret Irwin

There was once a powerful Enchanter of the name of Aldebaran, who had wearied of playing with the lives of men and retired to a palace he had built at the edge of the sea. The palace was of black marble with a green vein, which made it appear as though green serpents were crawling over it. But this slightly unpleasant impression was corrected by the beautiful shape of the palace, which rose in domes and minarets like a cluster of pomegranates, of black pomegranates, green-veined, each one barbed as with a crown.
It is a popular superstition that all enchanters are old, crooked, and hideous, and it is true that many of them do not attain their highest powers until they have outworn all that makes power worth while. But Aldebaran was of such dignified stature and ageless appearance that it was held, first that he was a King who had abnegated his royal power for one yet more extensive, and second, that he had discovered the Elixir of Eternal Youth. He admitted this last, but with a gesture towards his daughter, Melusine, for he had discovered that in her, more than in all his spells, lay the secret of eternal youth.