I had earlier asked a question on Indra taking away a wheel from Surya's chariot and from the answer by Pushkar it turned out that he had done that to help his friend Rishi Etesha:
There was certain vedic Rishi named Etesha. Long time ago he was competing/fighting with surya. Surya was riding in his chariot at that time. When Surya's chariot was coming from the front of the Rishi, Indra stopped the chariot and pulled one wheel of his chariot to protect Rishi Etesha. And later with this wheel did slayed his foes. So Indra did took away the wheel to protect Rishi Etesha as well as with it to slay his enemies.
I want to know who was this rishi, how was he friends with Indra and what led to this race between him and the sun-god?