Tapasya To Brahma
Following his initial training, Ravana performed an intense penance (or tapasya) to Brahma (the Creator God), lasting several years. During his penance, Ravana chopped off his head 10 times as a sacrifice to appease brahma. Each time he sliced his head off a new head arose, thus enabling him to continue his penance. At last, Brahama, pleased with his austerity, appeared after his 10th decapitation and offered him a boon. Ravana asked for immortality, which Brahma refused to give, 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 known as 'Dasamukha' (Dasa = ten, mukha =face).
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