Indrota was an ancient ṛṣi (rishi; sage). He was a sage belonging to the vaṁśa (vamsa; clan or genealogical line) of Śunaka (Sunaka), so he was famous as Indrota Śaunaka (Saunaka). In the legend described in Śāntiparva of Mahābhārata, it is said that Indrota became the priest of the yajña (yajna) performed by the ancient king Pārikṣhit (Parikshit) Janamejaya, belonging to the Puru clan.
[See Janamejaya – 1]
However, the earliest references of Indrota Śaunaka, priest of Janamejaya can be found in the ancient Brāhmaṇa texts. In Śatapatha Brāhmaṇa (Satapatha Brahmana) , he is mentioned as Indrota Daivāpa (Daivapa) Śaunaka. But it is not very clear how he was connected to Devāpi (Devapi), genealogically or through the line of disciples.
In Śāntiparva (Santiparva) of Mahābhārata(Mahabharata) it is described that Pārikṣit(Parikshit) Janamejaya was a very just king, but once, unintentionally, he committed a sin of Brahmahatyā (Brahmahatya; killing a Brahmana). When the sin of Brahmahatyā came upon the king, all his priests, ministers, and subjects renounced him. The king himself, in utter repentance, left the kingdom and started roaming about the forest. He asked the forest-dwelling tapasvīs the way to get rid of this sin, but nobody helped the cursed king. In this way, Janamejaya reached the hermitage of ṛṣi (rishi; sage) Indrota, who immediately rebuked Janamejaya in harsh words — “The sin you have committed is worse than Brahmahatyā. Why have you come to my hermitage, with your sin-infested body? My hermitage is also stained with your present. The very sight of you is harmful.” Thus rebuffed by Indrota, king Janamejaya humbly said, “Whatever you have said, is true. I deserve such condemnation. But I have come to you with great hope, to get a way out of my sin. Kindly advice me so that I can be free of this sin. Let not the great royal line, in which I am born, perish due to my sin.” Indrota got pleased with this humility of and repentance of Janamejaya, and gave him long advices for getting rid of his sin. He advised Janamejaya to perform several religious and beneficial acts for the peoples’ good. He said, “O king, if someone feels repentant after committing a sin, and in that situation, if that person takes resolution for some great action for public benefit, and afterwards performs the aśvamedha yajña (aswamedha yajna, a kind of Vedic ritual in which a horse is to be offered as sacrifice), that person is freed from all heinous sins”. Under the instructions of sage Indrota, Janamejaya performed aśvamedha yajña, and Indrota himself acted as the priest. As a result, the king got liberated from all his sins.