The following folk-tale purports to give an account of the origin and propagation of U Thlen, the most remorseless and cruel of all the Khasi deities.

According to tradition the Hima (state) of Cherra was, in olden times, the haunt of many famous Bleis (gods) who dominated the lives of men. These deities were said to dwell in certain localities, which in consequence came to be recognised as sacred places, and frequently to be called after the names of the Bleis. Foremost among these gods was U Mawlong Siem, and the hill where he was supposed to dwell is called after his name to the present day, and the inhabitants of certain villages still offer sacrifices to him.

In common with mankind, U Mawlong Siem is described as having a family, who, also in common with mankind, took pleasure in dancing and festivity. It is said that people sometimes hear the sound of revelry and the beating of drums within the mountain, supposed to be the drums of U Mawlong Siem beaten to the accompaniment of the dancing of his children, the sound of which invariably portends the death of a Siem or some great personage.

The only one of his family whose name and history have been transmitted was a daughter called Ka Kma Kharai, which signifies one that roams about in trenches or hidden nooks. She was well known in the Blei-world, and she possessed the power of assuming whatever form she pleased. She often assumed the form of a woman and mingled with mankind without anybody suspecting her identity. Many of the Bleis sought her in marriage, but U Mawlong Siem, her father, would never give his consent, lest his prestige be lowered among the Bleis.

There was one suitor whom Ka Kma Kharai specially favoured. He was the god of Umwai, but her father forbade the union so sternly as to dispel all the hopes of the lovers. This so angered the young goddess that henceforth she rebelled openly against her father, and by way of retaliation she encouraged the attentions of strange and undesirable lovers.

The Haunt of Ka Kma Kharai.

When it was discovered that she was with child, she fled from her home, fearing the wrath of her father, and put herself under the protection of her maternal uncle, who lived in the Pomdoloi cave, and was one of the famous dragons, or Yak Jakors of the country. In this cave a son was born to her, who proved to be a monster of hideous aspect, having the form of a snake and the characteristics of a vampire, who could be appeased only when fed with human blood. This monster they called U Thlen.

Unlike his mother, U Thlen could not transform himself into any likeness but that of a snake, but he had power to diminish or to enlarge his size at will. Sometimes he appeared so small as to be no bigger than a string of fine thread, at other times he expanded himself to such dimensions that he could swallow a man bodily.

In those days there was much intercourse between the Bleis and mankind. The latter were privileged to attend the Iew-blei—the fair of the Bleis—at Lynghingkhongkhen, the way to which passed the Pomdoloi cave, and many unwary and unprotected travellers fell a prey to the greed of U Thlen and his associates.