A prajapati. Once Brahma wanted to conduct a yajna but could not find a ritwik. He decided to create one in his mind. A thousand years later he sneezed and the ritwik was born and this was Kshupa. brahma made him a ritwik and conducted the yajna as per Mahabharat Shantiparva Chapter 122. Rudra made him the prajapati of all living beings.