Naturally, as a link between these supernatural worlds and the natural world, there arose a body of men and women in Irish legend who, by years of study, gained a knowledge of, and power over, the supernatural beings, and used these powers for hurt to the enemies of their kingdom, or for help to their own people.  Some were wise, learned, and statesmanlike, and used their powers for good.  These were the high Druids, and every king had a band of them at his court and in his wars.  They practiced what the Middle Ages called white magic.  Others were wizards, magicians, witches, who, like the children of Cailitin, the foes of Cuchulain, or the three mutilated women whom Maev educated in evil craft to do evil to her foes, or the dread band that deceived Cuchulain into his last ride of death, practised black magic—­evil, and the ministers of evil.  Magic, and the doing of it, runs through the whole of Irish story-telling, and not only into pagan but also into Christian legend; for it was easy to change the old gods into devils, to keep the demonic creatures as demons, to replace the wise Druids by the priests and saints, and the wizards by the heretics who gave themselves to sorcery.  Thus the ancient supernaturalism of the Irish has continued, with modern modifications, to the present day.  The body of thought is much the same as it was in the days of Conor and Finn; the clothing is a bit different.

Another characteristic of the stories, especially in the mythological period, is the barbaric brutality which appears in them.  Curiously mingled with this, in direct contrast, is their tenderness.  These extreme contrasts are common in the Celtic nature.  A Gael, whether of Ireland or the Western Isles, will pass in a short time from the wildest spirits, dancing and singing and drinking, into deep and grim depression—­the child of the present, whether in love or war; and in the tales of Ireland there is a similar contrast between their brutality and their tenderness.  The sudden fierce jealousy and the pitiless cruelty of their stepmother to the children of Lir is set over against the exquisite tenderness of Fionnuala, which pervades the story like an air from heaven.  The noble tenderness of Deirdre, of Naisi and his brothers, in life and death, to one another, is lovelier in contrast with the savage and treacherous revenge of Conor.  The great pitifulness of Cuchulain’s fight with his dear friend Ferdia, whom he is compelled to slay; the crowning tenderness of Emer’s recollective love in song before she dies on Cuchulain’s dead body, are in full contrast with the savage hard-heartedness and cruelties of Maev, and with the ruthless slaughters Cuchulain made of his foes, out of which he seems often to pass, as it were, in a moment, into tenderness and gracious speech.  Even Finn, false for once to his constant courtesy, revenges himself on Dermot so pitilessly that both his son and grandson cry shame upon him.