Complex sentence: During the "Devasura Sangram" (the battle between the devas and the asuras) he defeated Indra, tying him up and mounting him onto his celestial chariot.
Split into simpler sentences: During the "Devasura Sangram" (the battle between the devas and the asuras). He then turned the tables on Indra, tying him up and mounting him onto his celestial chariot.