The Mythology & Folklore Database
Like all goblins of this class, the Ellylldan was, of course, seen dancing about in marshy grounds, into which it led the belated wanderer; but, as a distinguished resident in Wales has wittily said, the poor elf "is now starved to death, and his breath is taken from him; his light is quenched for ever by the improving farmer, who has drained the bog; and, instead of the rank decaying vegetation of the autumn, where bitterns and snipes delighted to secrete themselves, crops of corn and potatoes are grown."...
Pwca, or Pooka, is but another name for the Ellylldan, as our Puck is another name for the will-o'-wisp; but in both cases the shorter term has a more poetic flavor and a wider latitude.... The most familiar form of the Pwca story is one which I have encountered in several localities, varying so little in its details that each account would be interchangeable with another by the alteration of local names. This form presents a peasant who is returning home from his work, or from a fair, when he sees a light traveling before him. Looking closer he perceives that it is carried by a dusky little figure, holding a lantern or candle at arm's length over its head. He follows it for several miles, and suddenly finds himself on the brink of a frightful precipice. From far down below, there rises to his ears the sound of a foaming torrent. At the same moment the little goblin with the lantern springs across the chasm, alighting on the opposite side; raises the light again high over its head, utters a loud and malicious laugh, blows out its candle, and disappears up the opposite hill, leaving the awestruck peasant to get home as best he can.