Khalis repays the prince for his kindness by changing into a snake and sucking the poison from the king’s daughter, from a Tuti-nama (Tales of a Parrot): Eighteenth Night

The prince looks on in amazement as his snake companion resumes his original form and saves the life of the princess, who was dying from a poisonous snake bite. The snake owed the prince a favor, since the prince had cut a piece of his own flesh to feed him and his mate. After the girl was restored to health, the prince married her and became viceroy to the king. His three companions, Good Fortune, the snake, and the frog, having fulfilled their obligation, then bid him farewell.