Vibhishana is the younger half brother of Ravana, the ten-headed demon king of Lanka. Of noble character, he advised Ravana - who had abducted Sita - to return her promptly and properly to her husband, Rama.
When Ravana refused to heed his advice, Vibhishana joined Rama’s army and after Rama defeated Ravana, was crowned king of Lanka.
In the killing of Ravana by Rama, Vibhishana also played a crucial role, for it was he who revealed the secret of Ravana’s vulnerability. He told Rama that Ravana would die only if attacked on his navel and it was when Rama targeted Ravana there that he fell.
In the sharing of this secret, however, some doubt is cast on Vibhishana’s noble character, for it can be read as a betrayal of brotherly bonds and loyalty.