Ravana is depicted and described as having ten heads and is considered to be most revered devotee of Shiva, a great scholar, a capable ruler and a maestro of the veena, but someone who wished to overpower the devas.

Ravana is depicted and described as having ten heads and is considered to be most revered devotee of Shiva, a great scholar, a capable ruler and a maestro of the veena, but someone who wished to overpower the devas. His ten heads represent his knowledge of the six shastras and the four Vedas. Ravana was author of the Ravana Samhita, a book on Hindu astrology, and also Arka Prakasham, a book on Siddha medicine and treatment. He was a master of 64 types of knowledge and all arts of weaponry. He is said to have possessed the nectar of immortality, which was stored inside his belly, thanks to a celestial boon by Brahma. Ravana performed an intense penance lasting several years and asked for immortality from Brahma, who refused, but gave him the celestial nectar of immortality. The nectar of immortality, stored under his navel, dictated that he could not be vanquished for as long as it lasted. Ravana also asked for absolute invulnerability from and supremacy over gods, heavenly spirits, other rakshas, serpents, and wild beasts. Contemptuous of mortal men, he did not ask for protection from these. Brahma granted him these boons in addition to his 10 severed heads and great strength by way of knowledge of divine weapons and magic. Thus Ravana is known as 'Dasamukha' (ten faced) or 'Dashaanan' or Dasagriva (ten headed)

As per one interpretation, Ravana’s 10 heads are the 10 emotions or senses in a human:
Kaam (lust)
Krodha (anger)
Moha (delusion)
Lobha (greed)
Mada (pride)
Maatsarya (envy)
Manas (the mind)
Buddhi (intellect)
Chitta (will), and
Ahamkara (ego)
Hindu traditions emphasize on the importance of controlling one’s senses and projecting just the intellect alone, which is considered supreme over others. The use of other emotions are considered to be detrimental to the growth of a soul. The great king Mahabali advised Ravana to shun these nine emotions and to keep only intellect to which Ravana justifies that the possession of all these facets are equally important and make him a complete man.

The head controls our destiny and the ten 10 heads of Ravana controlled his actions which ultimately led to his destruction. The king of Lanka became a slave to his senses and since he could not control his desires, he not only destroyed himself and his clan but the whole Lanka was reduced to ashes as well. Having all this knowledge and not being unable to harness his powers was one of Ravana’s biggest regrets as he lay dying on his deathbed.!!