We cite here an extract from an introduction by Denis Florence
MacCarthy to his translation of Calderon's "Purgatory of St. Patrick."
It will be of interest as following the thread of this weird legend:

The curious history of Ludovico Enio, on which the principal interest of this play depends, has been alluded to, and given more or less fully by many ancient authors. The name, though slightly altered by the different persons who have mentioned him, can easily be recognized as the same in all, whether as Owen, Oien, Owain, Eogan, Euenius, or Ennius. Perhaps the earliest allusion to him in any printed English work is that contained in 'Ranulph Hidgen's Polychronicon,' published at Westminster by Wynkin de Worde, in 1495: 'In this Steven's tyme, a knyght that hyght Owen wente into the Purgatory of the second Patrick, abbot, and not byshoppe. He came agayne and dwelled in the abbaye of Ludene of Whyte Monks in Irlonde, and tolde of joycs and of paynes that he had seen.'

The history of Enio had, however, existed in manuscript for nearly three centuries and a half before the Polychronicon was printed; it had been written by Henry, the Monk of Salterey, in Huntingdonshire, from the account which he had received from Gilbert, a Cistercian monk of the Abbey of the Blessed Virgin Mary of Luden, or Louth, above mentioned. [1] Colgan, after collating this manuscript with two others on the same subject, which he had seen, printed it nearly in full in his "Trias." … Matthew Paris had, however, before this, in his "History of England," under date 1153, given a full account of the adventures of OEnus in the Purgatory. … Sir Walter Scott mentions, in his "Border Minstrelsy," that there is a curious Metrical Romance in the Advocates' Library of Edinburgh, called "The Legend of Sir Owain," relating his adventures in St. Patrick's Purgatory; he gives some stanzas from it, descriptive of the knight's passage of "The Brig o' Dread;" which, in the legend, is placed between Purgatory and Paradise. This poem is supposed to have been written early in the fourteenth century.

[Footnote 1: Colgan's "Trias Thanmaturgæ," p. 281, Ware's "Annals of
Ireland," A.D. 1497.]

A second extract on the subject, taken from the Essay by Mr. Wright on the "Purgatory of St. Patrick," published in London in 1844, gives still further information with regard to it.

"The mode," he says, "in which this legend was made public is thus told in the Latin narrative. Gervase (the founder and first Abbot of Louth, in Lincolnshire) sent his monk, Gilbert, to the king, then in Ireland, to obtain a grant to build a monastery there. Gilbert, on his arrival, complained to the king, Henry II., that he did not understand the language of the country. The king said to him,' I will give you an excellent interpreter,' and sent him the knight Owain, who remained with him during the time he was occupied in building the monastery, and repeated to him frequently the story of his adventures in Purgatory. Gilbert and his companions subsequently returned to England, and there he repeated the story, and some one said he thought it was all a dream, to which Gilbert answered: 'That there were some who believed that those who entered the Purgatory fell into a trance, and saw the vision in the spirit, but that the knight had denied this, and declared that the whole was seen and felt really in the body.' Both Gilbert, from whom Henry of Salterey received the story, and the bishop of the diocese, assured him that many perished in this Purgatory, and were never heard of afterwards." It is clear from the allusion to it in Cæsarius of Heisterbach, that already, at the beginning of the thirteenth century, St. Patrick's Purgatory had become famous throughout Europe. 'If any one doubt of Purgatory,' says this writer, 'let him go to Scotland (i. e., Ireland, to which this name was anciently given), and enter the Purgatory of St. Patrick, and his doubts will be expelled.' This recommendation was frequently acted upon in that, and particularly in the following century, when pilgrims from all parts of Europe, some of them men of rank and wealth, repaired thither. On the patent rolls in the Tower of London, under the year 1358, we have an instance of testimonials given by the king, Edward III., on the same day, to two distinguished foreigners, one a noble Hungarian, the other a Lombard, Nicholas de Becariis, of their having faithfully performed this pilgrimage. And still later, in 1397, we find King Richard II. granting a safe conduct to visit the same place to Raymond, Viscount of Perilhos, Knight of Rhodes, and Chamberlain of the King of France, with twenty men and thirty horses. Raymond de Perilhos, on his return to his native country, wrote a narrative of what he had seen, in the dialect of the Limousin (Lemosinalingna), of which a Latin version was printed by O'Sullivan in his '_Historia Catholica Ibernica.' … This is a mere compilation from the story of 'Henry of Salterey,' and begins, like that, with an account of the origin of the Purgatory. He represents himself as having been first a minister to Charles V. of France, and subsequently the intimate friend of John I. of Aragon, after whose death (in 1395) he was seized with the desire of knowing how he was treated in the other world, and determined, like a new Æneas, to go into St. Patrick's Purgatory in search of him. He saw precisely the same sights as the knight, Owain, but (as in Calderon) only twelve men came to him in the hall instead of fifteen, and in the fourth hall of punishments he saw King John of Aragon, and many others of his friends and relations.

We will now select from the drama of "Calderon" a few characteristic passages, to show how this subject was treated by the glowing pen and fervid fancy of the greatest of all the poets of Catholic Spain, whose poetry, indeed, is deserving of more widespread appreciation than it has yet received at the hands of the Catholic reading public. We will begin with those lines in which Ludovico Enio, the hero of the tale, makes known his identity to King Egerio.

LUDOVICO. Listen, most beautiful divinity,
For thus begins the story of my life.
Great Egerio, King of Ireland, I

Am Ludovico Enio—a Christian also—
In this do Patrick and myself agree,
And differ, being Christians both,
And yet as opposite as good from evil.
But for the faith which I sincerely hold
(So greatly do I estimate its worth),
I would lay down a hundred thousand lives—
Bear witness, thou all-seeing Lord and God.

. . . . . . All crimes,
Theft, murder, treason, sacrilege, betrayal
Of dearest friends, all these I must relate.
For these are all my glory and my pride.
In one of Ireland's many islands I
Was born, and much do I suspect that all
The planets seven, in wild confusion strange,
Assisted at my most unhappy birth.