A sage, who was the son of Brahma. He was supremely knowledgeable, and became the guru of Nidakha, son of Pulastya and grandson of Brahma. He taught Nidakha everything – scriptures to weaponry, but realised he was not interested in Advaita, and was disappointed. Pulastya built a beautiful city on the banks of the river Devika named Viranagara, and that was where Nidakha lived. After Nidakha had lived there for a thousand years, his guru visited him. He stood on the steps so that Nidakha would see him when he came out to greet his guests. Nidakha greeted him warmly and after taking him inside, washed his feet, and invited him to eat. Ribhu said he preferred something sweet and Nidakha’s wife promptly prepared it. After the meal, Nidakha asked Ribhu  whether the meal was satisfying and where he was going. Ribhu replied that only a hungry man could be satisfied and that he wasn’t hungry. He also said that the question on destination was irrelevant since man never stayed anywhere nor did he leave. The body was made of the five elements and when they left, it would cease to exist. Nidakha became a believer in God then.

After another thousand years, Ribhu visited again and found Nidakha outside the city, as a sage, and they both stood aside  as the king’s procession passed. Then the following conversation happened

Nidakha: The king is entering his city, hence the huge procession.

Ribhu: Who is the king among these people, and who are the subjects?

Nidakha: The man who sits atop the mighty elephant is king, and the rest are his subjects.

Ribhu: You pointed to the king and the elephant. Which is the elephant and which, the king? What are their distinguishing features?

Nidakha: The creature at the bottom is the elephant, the other is the king.

Ribhu: What is bottom, and what is up?

Nidakha quickly climbed on Ribha and said, “Where I sit is ‘up’ and you’re at the bottom”

Ribhu: If you’re like the king and I’m like the elephant, who am I and who are you?

Nidakha recognised his guru and bowed to the advaita knowledge. Ribhu left and Nidakha became a believer of advaita. From then on, he considered all creatures no different from him. He later attained moksha as per Vishnupurana Ansh 2 Chapters 15-16.