An ancient King who lived on vegetable food only.
[M.B. Anuśāsana Parva, Chapter 115, Stanza 66] .
DHUNDHU I A notorious Asura. He was the son of the Madhu Kaiṭabhas. Brahmā was born in the lotus from the navel of Viṣṇu, who was lying in meditation on the surface of water. From the ear-wax of Viṣṇu two asuras--Madhu and Kaiṭabha sprang up. They terrified Brahmā by shaking the stalk of the lotus. Brahmā became terribly afraid of the asuras and ran about on the surface of water. Hearing the cry of Brahmā Viṣṇu awoke, but he could not defeat the asuras. Viṣṇu decided to employ ‘Sāma’ (conciliation) the first expedient. The arrogant demons ordered Viṣṇu to ask of them any boon. Viṣṇu replied. “If it is so, you must be killed by me.” They could not but give the boon. They agreed to the request of Viṣṇu and said: “But we must be killed in an atmosphere, which is not cloudy.” Viṣṇu killed them when the atmosphere was clear. A son named Dhundhu had been born to Madhu and Kaiṭabha. Because Viṣṇu had killed his fathers Dhundhu decided to take revenge on Viṣṇu and the Gods. With this idea in view Dhundhu began to do penance in the sandy desert of Ujjālaka in Marudhanva. Standing on one leg he did penance for thousands of years. Then Brahmā appeared before him and gave the boon that he would not be killed by Devas, Dānavas (asuras), Gandharvas (Demi-gods), Rākṣasas (demons), Yakṣas (paragods) and Uragas (serpents). Having got this boon, he lived under sand in the desert of Ujjālaka. His idea was to destroy the gods. A hermit named Uttaṅka had erected his hermitage in another part of Marudhanva and began penance. By his penance he made Viṣṇu appear before him and then made a request that Dhundhu's activities be put a stop to. Viṣṇu replied “Uttaṅka! Dhundhu has become a curse to the three worlds. There is a king named Kuvalāśva, born of the dynasty of Ikṣvāku. He will kill Dhundhu.” Saying these words, Viṣṇu disappeared. Uttaṅka went to the palace of Kuvalāśva and told him what Viṣṇu had said. Kuvalāśva and his sons went to the forest and killed Dhundhu in a fight. From that day Kuvalāśva came to be known by the name Dhundhumāra, which meant ‘the killer of Dhundhu.
[M.B. Vana Parva, 4 Chapters from 201] .
Note: 1. Dhundhu was the son of Kaśyapa, born of Danu. It was to kill Dhundhu that Viṣṇu incarnated a Vāmana, Vāmanapurāna Chapter 8.]