Ravana was one of the important characters in Ramayana! He played the role of a villain in it but barely anyone knows that it was a blessing in disguise for him. In his previous life, he was the guard (dwarapala) of Lord Vishnu who was cursed by the Sanata kumaras. Once Sanatakumars went to Vaikuntha to see Lord Vishnu. But Jay and Vijay, the two guards of Lord didn't let them in. Thus, out of anger, they said, ‘O Jay and Vijaya! Both of you will be born in Rakshas yoni (as demons) on the earth as you disobeyed us.’
Having heard the curse, Jay and Vijay pleaded to Lord Vishnu to release them from the Brahmins’ curse. Lord Vishnu felt pity for his devotees. He gave them a choice saying, ‘O dears! Brahmin curse can't be futile. Either you have to take three births as my bitter enemy and will be killed by me or you will complete seven births as normal good humans and my devotees and finally come to my abode. Choose one among these two options.’ But Jaya and Vijaya chose the former as they didn't want to be separated from their lord for a long time. Thus, in Treteya yug, Ravana and Kumbhakarna took their birth as demons.
Ravana was the grandson of one of the greatest sages Pulastya and the son of the great Sage Vishrava. His mother was a demon princess. Thus, Ravana was half Brahmin and half demon. He was a great devotee of Lord Shiva. Through his severe penances, Ravana also pleased Lord Brahma. He was blessed with invincibility and had the power to assume any form he wished. With time, Ravana became greedy and arrogant, casting his eyes on a beautiful land- Lanka, an island created by celestial architect Vishwakarma for his half-brother, Kubera. He took it by force.
He was considered one of the best rulers and he was an expert in playing Veena. He was well-versed in the Veda and Vedangas and all the scriptures. He had mastered astrology and Ayurvedic medicine. He had written two beautiful books- Ravana Samhita and Ark Prakasham. It is said that he was so powerful that he could control the positions of the planets at his will. Being a demon king, he had mastered Tantra Vidya and black magic which he used against his foes in the battle.
Ravana was an ardent devotee of Lord Shiva. He performed severe penances to please Lord Shiva and cut off his head ten times as a sacrifice. At last, Lord Shiva was pleased with his Tapashya and offered him a boon. Ravana asked Lord Shiva to grant him immortality but that was not granted by the Lord. His arrogance went to that level once he wished to lift the Kailash mountain- the abode of Lord Shiva and Parvati! Beholding his excess vanity, Lord Shiva wished to teach him a lesson. When Ravana tried to lift the Kailash mountain, Lord Shiva put his toe on the top of the mountain. Thus, Ravana’s forehand was crushed under it and he screamed aloud causing severe pain. His roaring sound was so loud that it was heard all over the three worlds. Hence, he was called Ravana which means roaring. He understood his own mistake and started chanting the praise of Lord Shiva. Lord Shiva was so pleased with Ravana that he started a terrible dance which was later called Tandava Nritya. And the shlokas he chanted called- Shiva Tandava Stotram! In present-day society, Shiva Tandava stotram has occupied the hearts of millions!
His ten heads symbolized six shastras and four Vedas. In some other Puranas, it said that his ten heads stand for ten emotions- anger, lust, greed, and other negative attributes. He was brilliant. He had mastered all weaponry. At one point, Ravana became so powerful and egoistic that he lost his mind to pay respect to the words of his well-wisher. Once, mighty king Bali told him, ‘O Ravana! Reject the nine heads and follow only one head- intellect! You can attain everything with that.’
Ravana retorted to Bali saying, ‘O king Bali! All the heads are equally important to me. That makes me a complete man!’ Being blessed by Lord Shiva and Lord Brahma, Ravana behaved atrociously without using his intellect. He couldn't control his sense organs. He became lustful, wrathful, and desirous which ultimately brought his destruction. Because of his self-interest, Lanka was burnt to ashes! He was so learned and having all the knowledge he was not able to harness his wisdom. At the time of his death, he regretted his foolishness.
Since Ravana was one of the most learned scholars and true devotees of Lord Shiva, Lord Rama asked Lakshmana to go near Ravana and get some knowledge. Whatever Ravana taught him, the most important lesson was- Never to underestimate your enemy in any circumstance!