On one hand, Vishwaroopa helped the Devatas perform many powerful Yagnas and on the other he was gifting away a portion of those Yagna results to the demons. Due to helping the Devatas, he attained great repute amongst the Devatas. Due to gifting these results to demons, even among the demons he was revered and respected.
Vishwaroopa’s popularity amongst the demons puzzled Indra. His unending fame was also a little irritating nevertheless, Indra could not fathom the reason behind it. However, one fine morning Maharishi Narada arrived and informed Indra the secret behind this fame achieved by Vishwaroopa. In fury, Indra instantly chopped off all the 3 heads of Vishwaroopa. Indra was now tainted with the sin of murdering his Guru (Guru hatya). Since Guru is Brahma, killing Guru was Brahmahatya.
It was around this time that the atrocities of demon Vrittasura reached the zenith. Indra who now did not have the help of Guru could not face this demon. Yet, with the help of Maharishi Dadhichi and with the thunderbolt weapon (vajrayudha) thus obtained, Indra managed to kill Vrittasura.
Vrtta was a Brahmin and hence, Indra was now tainted with another sin. Indra who lacked Guru’s support could no longer withstand these sins that chased him. He had abandoned his first Guru and has killed his second Guru. So how could he have any support from Guru? Helpless, he deserted heaven and hid in a lotus stalk in a pond, wherein he resided for 10000 years. This was the outcome of abandoning his Guru.
During this absence of Indra from heaven, Nahusha assumed the position of Indra and ruled. This Indra who hid in the pond composed many hymns and prayed earnestly. Only when people are beleaguered by troubles, they begin to chant holy hymns, Sahasranamas, Trishati, Guru gita etc. They strive to understand the meanings contained in all these hymns.
Likewise during this period Indra too composed many Kavacha mantras, hymns in praise of Mother Lakshmi, Datta etc