In The Colloquy with the Ancients, as St. Patrick and Caoilte are talking with one another, a lone woman robed in mantle of green, a smock of soft silk being next her skin, and on her forehead a glittering plate of yellow gold, came to them; and when Patrick asked from whence she came, she replied: “Out of uaimh Chruachna, or ‘the cave of Cruachan’.”
Caoilte then asked: “Woman, my soul, who art thou?”
“I am Scothniamh or ‘Flower-lustre’, daughter of the Daghda's son Bodhb derg.”
Caoilte proceeded: “And what brought thee here?”
“To require of thee my marriage-gift, because once upon a time thou promised me such.”
And as they spoke Patrick broke in with: “It is a wonder to us how we see you two: the girl young and invested with all comeliness; but thou Caoilte, a withered ancient, bent in the back and dingily grown grey.”
“Which is no wonder at all,” said Caoilte, “for no people of one generation or of one time are we: she is of the Tuatha Dé Danann, who are unfading and whose duration is perennial I am of the sons of Milesius, that are perishable and fade away.”
The exact distinction is between Caoilte, a withered old ancient - in most ways to be regarded as a ghost called up that Patrick may question him about the past history of Ireland - and a fairy-woman who is one of the Sidhe or Tuatha Dé Danann.