Esclados the Red was the lord of Landuc, a castle and domain that lay hidden deep within the forest of Broceliande, the enchanted wood in Brittany where Merlin was said to be imprisoned by the fairy Nimue and where the rules of ordinary reality did not always apply. His castle stood near a magic spring, the fountain of Barenton, which possessed a power so ancient that it predated the Arthurian age itself. When a traveller poured water from the spring onto a stone slab, a perron, set beside it, the sky would darken, clouds would gather, and a terrible storm would burst upon the forest, with wind and rain and thunder so violent that no tree, no beast, and no dwelling within miles could escape its fury. The custom was old, older than Esclados himself, for his seneschal would later reveal that the guardianship of the spring had been maintained for sixty years, a span that suggested Esclados was not the first knight to hold the post but the latest in a long line of champions who had sworn to defend the waters and the lands they nourished.

The first recorded encounter with Esclados came through Calogrenant, a knight of King Arthur's Round Table and the cousin of Yvain. Calogrenant had heard of the marvel from a peasant in a remote castle, and he rode alone into Broceliande to test the spring for himself. He found the fountain in a clearing of marvellous beauty, with the stone slab beside it and a golden basin hanging from the branch of an evergreen tree. A peasant who tended the place warned him that the spring was guarded by a knight who would punish any man who disturbed it, but Calogrenant, proud and eager for adventure, poured the water onto the slab. At once the sky grew black, the wind howled, and the storm broke upon the forest. From the wood came Esclados, riding in full red armour, his shield blazing and his lance lowered. The two knights charged each other, and after a fierce exchange of blows Calogrenant was unhorsed and defeated. Esclados, however, proved himself a generous conqueror. Instead of taking Calogrenant prisoner or killing him, as chivalric custom would have allowed, he took only the knight's horse and sent him back to Arthur's court on foot, covered in shame but alive.

When Calogrenant told his tale at a Pentecost feast at Camelot, the court laughed at his humiliation, and Yvain, his cousin, swore to avenge the disgrace. Yvain rode alone to Broceliande, found the spring, and poured the water onto the stone slab just as Calogrenant had done. The storm came again, blacker and more violent than before, and from the forest rode Esclados the Red, furious that another stranger had dared to summon the tempest. The two knights met in combat, and the duel was long and terrible. Both fought with such skill that neither could gain the upper hand, and both took care, in a display of chivalric honour, not to strike each other's horses, a courtesy that set them apart from less noble warriors. They hacked at each other's shields and armour until the field was littered with splinters of wood and broken lances. At last Yvain struck a blow of such force that he shattered Esclados's helmet, splitting it down to the nosepiece and driving the blade into the knight's skull. Esclados was mortally wounded.

The dying knight did not fall. He turned his horse and fled toward his castle, spurring the animal through the forest with Yvain hard upon his heels. They reached the bridge before the castle gates, and Esclados managed to get across, but Yvain followed so closely that he too passed onto the bridge before the defenders could raise the drawbridge. The portcullis fell behind Yvain, trapping him between two iron grilles, a prisoner in the very castle he had conquered. Esclados rode inside and collapsed. He died within the walls of Landuc, leaving his widow Laudine to mourn him with a grief so profound that she tore her hair, clawed at her face, and swore vengeance upon the man who had killed her husband. Yvain, trapped between the portcullises, looked through the bars and saw Laudine for the first time, and in that moment of her greatest anguish he fell in love with her, a love that would drive him to madness and redemption and make him the Knight with the Lion.

Esclados's death did not end his story. The custom he had kept for sixty years demanded a new guardian, and Lunete, the clever maidservant who had hidden Yvain with a magic ring of invisibility, persuaded Laudine that the very knight who had slain her husband was the only man worthy to replace him. Yvain married Laudine and became the new defender of the spring, but the shadow of Esclados hung over the marriage. In the Welsh version of the tale, Owain, or the Lady of the Fountain, the corresponding figure is simply the Black Knight, unnamed and more ominous than the French original. In Hartmann von Aue's German adaptation Iwein, written at the same time as Chretien's poem, Esclados appears as a figure of equal stature, and the duel is even more elaborately described. The scholar Phyllis Ann Karr noted a curious paradox: Esclados appears only AFTER the storm has already been summoned and the damage done, suggesting that his role was less to prevent the disturbance than to punish the disturber, a function more judicial than protective.