The figure and characteristics of Indra  as depicted in Mahābhārata-Rāmāyaṇa-Purāṇa is completely different from that of his acts and manners as described in  old Veda and Brāhmaṇa treaties. Indra in/of Veda  the greatest warrior, he is slaughter of Vṛtra, Namuci, Śuṣṇa, Cumuri, Dhuni, Śambara, Pripru, Vala, Arbuda, Kuyava — killing these dangerous demons/Asuras he is celibrated as a  greatly  honoured hero of Devaloka (Heaven) in Veda and  Brāhmaṇa books. Hundreds of his  deeds are appraised in Ṛgveda — Indra strengthened the painstriken  loose/weak Earth, created the Antarīkṣa, settled the Mountains, thundered the Sky, created Fire in the Cloud, he made the entire Viśva-bhuvana (World ) —

yaḥ pṛthivīṃ vyathamānāmadṛṃhat

yaḥ parvatān prakupitā aramṇāt.

yo antarīkṣaṃ vimame varīyo

yo dyāmyastabhnāt sa janāsa indraḥ.

In this ṛksūkta many  deeds of Indra are celebrated with much importance.  Various other deeds and virtues of Indra are hailed in the other sūktas,  in thousands  of mantravarṇas (letters of Mantra). Indra has become Devarāja King of Deities) from Deva,  who are the rivals there, list of their names is so big, so is the power and tactics to resist and  kill them — all that is in his control.

The devils and demons whom Indra defeated and destructed Śambara, Bala and Vṛtra were famous among them. It is  more curious than the description of repeated fight of Indra with  Śambara  that the demon named  Śambara  had hidden himself in a mountain, Indra  could caught  him after searching for forty years, it is so assumed 

ya Śambaraṃ parvateṣu kṣiyantaṃ

catvāriśyāṃ śaradyannavindat

About Śambarāsura, there are two other stories in Ṛgveda. Śambara had a hundred rocky-stony unenterable palaces which were destructed  by throwing thunder by Indra-

yaḥ śataṃ śambarasya puro vibhedāśmaneva pūrvīḥ/

Paṇḍitas proclaimed, the name ‘Purandara’ is famous for this fest of Indra in Mahābhārata-Rāmāyaṇa-Purāāṇa. Other power of Śambarāsura is Māyā (Dissimulation). Without  the power of Māyā or deceit it was not possible to hide himself for a long period of forty ears from Indra.  Śambara is marked as ‘Mahāmāya’ in Mahābhārata and the phrase Māyā of Śambara here stands as a proverb–

śambarasya ca yā māyā/

Ofcource Devarāja  Indra too has become a deceitful deity for killing suc