Who is Sibi from Gods, Demons, and Others and what is their importance?

One afternoon, as King Sibi feasted along the river's edge with his disciples, a small white dove dropped into his lap. The hawk who had been chasing it swooped down and demanded the king give him the dove. The king refused, claiming the dove had come to him for refuge. The hawk and the king argued until the king realized that the hawk would not be satisfied until he got fresh meat. The king then offered his own flesh instead of the dove's, whereupon the hawk turned into Indra, the chief of the gods, and the dove turned into the god of fire. King Sibi had passed the test that was designed to challenge his virtue as king and protector.