Most people only know about incarnations of Vishnu, and perhaps incarnations of Brahma (which I discuss here) and incarnations of Shiva. But Indra has also taken incarnations, for instance as Vishwamitra' father Gadhi. But my question is about the most famous incarnation of Indra in ancient times, Indra Vaikuntha.
Indra Vaikuntha's name has nothing to do with Vishnu's abode of Vaikuntha. Indra incarnated as the son of the demoness Vikuntha, and then he conquered the Asura races throughout the three worlds. But then, due to being in the body of an Asura, he forgot who he was and started tormenting the gods. He only regained his true identity when a sage known as Saptagu Angirasa held his hand and praised him with a hymn. Here is what this excerpt from the Brihaddevata, an ancient work by the sage Shaunaka, says:
There was an Asuri, daughter of Prajapati, Vikuntha by name. She, desiring a son like Indra, performed very severe austerities. She then obtained from Prajapati her desires (in the form of) various boons. And Indra himself was born of her, as he wished to slay the Daityas and Danavas. Once he was engaged in battle with the Danavas. Of them he slew nine nineties and seven groups of seven. Having shattered with the might of his arm the citadels of gold, silver, and iron, (and) having slain all (of them) in their respective spheres (yathasthanam), as arrayed on earth and the other (two worlds). On earth he exterminated both the Kalakeyas and the race of Puloma, the archer, and in heaven the notorious (tan) offspring of Prahlada.
Having obtained sovereignty among the Daityas (and) puffed up with pride by reason of his might, he began to harass the gods, being infatuated by the craft of the Asuras. Now while they were being harassed by that same Asura of unlimited power, they fled for succour to Saptagu, most excellent of seers, in order that the latter should admonish him (Indra). Now the seer called Saptagu was a dear friend of his, and (so) he praised him with the (hymn), 'We have grasped' (jagrbhma: x.47) as he took him be the hand. Then he coming to (buddhva) himself (and) rejoiced at the praise of Saptagu, praised himself with the three (hymns) 'I was' (aham bhuvam: x.48-50)[.]
And indeed, as you can see in the Rig Veda Anukramani in my answer here, Indra Vaikuntha is the seer of hymns 48-50 of Rig Veda Book 10, which are Atmastutis or hymns of self-praise. There's the Indra we know and love!
But my question is about the identity of the Saptagu Angirasa, the sags who helped Indra. Hymn 47 of Rig Veda Book 10 is the hymn that Saptagu told to Indra to make him remember who he really was, and in particular it says this:
pra saptaghuṃ ṛtadhītiṃ sumedhāṃ bṛhaspatiṃ matirachājighāti | ya āṅghiraso namasopasadyo.asmabhyaṃ citraṃvṛṣaṇaṃ rayiṃ dāḥ ||
To Saptagu the sage, the holy-minded, to him, Bṛhaspati, the song approaches,
Aṅgiras' Son who must be met with homage: vouchsafe us mighty and reslendent riches.
My question is, is this verse saying that Saptagu Angirasa is another name for Brihaspati, the guru of the gods?
It would certainly make sense considering that Brihaspati is the son of the sage Angiras as I discuss here. And epithets like "dear friend" of Indra and "most excellent of seers" sound fitting for Brihaspati. But why would Brihaspati be called "Saptagu"? According to this dictionary it means "driving seven oxen", and I'm not sure if Brihaspati is ever described in that way.
In any case, does anyone know scriptures that address the identity of Saptagu Angirasa? For instance, do the Puranas ever tell the story of Indra Vaikuntha?