He curses the Yaksha into a Brahmarakshas, promising his revival only upon teaching a human, the Mahabhashya.The Yaksha teaches it to Govindaswami, the father of Vararuchi, Vikramaditya, Bhatti and Bhartruhari.
Patanjali in his Mahabhasya regards the Shakas and Yavanas as pure Shudras (II.4.10).