Yag-Kosha is a being being from beyond the stars enslaved by the evil sorcerer Yara in his tower, keeping as source for his malevolent power. He is vaguely humanoid in form, having eyes, hands, legs, and a mouth capable of speech. His skin is leathery grey, like an elephant, and his head bears many features similar to elephants, such as tusks, large ears, and a trunk.
Long before the dawn of man, and before even the Hyborian age began on Earth, a conflict raged on the far-distant world of Yag. The noble and peaceful people retreated into exile across the stars, coming at last to Earth. Here they hid in the deep jungles, living simple lives of hunter-gatherers, and not interfering with the evolution and history of mankind. However, as time went by, more and more of the people died, and at last only Yag-Kosha remained. Deep in the jungles of Khitai, he adopted a tribe of humans, teaching them the ways of civilization and being worshipped as a god. Then one day Yag-Kosha met Yara. Yara was a student of lore and sorcery, and had come to Yag-Kosha to learn from the wise and knowledgeable alien. Yag-Kosha made an effort to teach Yara humility and morality, but the sorcerer was interested in only power. He betrayed his mentor, confining him and torturing him until he could draw more secrets of sorcery from the peaceful exile. Back in the west, he tortured Yag-Kosha and made him a magical slave, forcing him to construct the Elephant Tower and perform other deeds. In this time, over hundreds of years, he withered from torture and confinement, and knew only suffering.
When the young barbarian Conan hears about the mysterious tower and goes to steal from its treasure, he meets Yag-Kosha, his confinement now left him blinded, withered and atrophied, with stick-thin limbs he cannot move. His body is marked with scars and burns from his many years of torture and torment. Helpless, he convinced Conan to slay him as part of a final spell which gave him revenge over the evil Yara, and in doing so, was reincarnated as Yogah of Yag. He destroyed the Elephant Tower, and flew away to parts unknown.