That Lord Shiva has many Forms,is a fact many are aware of.
The difference between the Forms of Lord Vishnu and Shiva is that in an Avatar, Lord Vishnu ,Avatar means coming down,Lord Vishnu is born and the lineage is found,whereas ,in the case of Shiva,it is not found.
He appears ,does what he has to do and disappears.
No one is completely evil or bad just as no one is completely Good.
Human nature is an admixture of both.
Spiritual development occurs when good tendencies prevail over evil.
And one becomes a better human being when he realizes his erroneous ways and reforms.
And God Blesses one when one has the good tendencies prevailing.
Ravana was a good King, administrator,pious and a learned Brahmin.
His two failings,
Ego and lusting after another’s wife.
For his latter failing he was killed and his act wiped out all his other good qualities.
Because of his monumental Ego he once tried to move the Abode of Lord Shiva,Kailash.
Shiva pressed down his little toe and his hands were crushed and he was caught underneath the mountain.
He recited the Sama Veda to please Shiva.
Shiva appeared and granted him the powerful Sword Chandrahasa.
Ravana praised Shiva by composing Shiva Tandava Stotra.
nother version in Tamil is that Ravana played Sama Tasha in his Veena,a string instrument.
The Form of Shiva that blessed Ravana is called Ravana Anugrahamurthy.
This is depicted in Colorado Caves,Cave Number 21.
I recollect having seen this Form of Shiva in many Shiva temples in South India,though I am unable to recollect them off hand.
‘The Uttara Kanda of the Hindu epic Ramayana records: the ten-headed, twenty-armed mighty King Ravana defeated and looted Alaka – the city of his step-brother and god of wealth Kubera, situated near Mount Kailash. After the victory, Ravana was returning to Lanka in the Pushpaka Vimana (the flying chariot stolen from Kubera), when he spotted a beautiful place. However, the chariot could not fly over it. Ravana met Shiva’s bull-faced dwarf attendant Nandi (Nandisha, Nandikeshvara) at this place and asked the reason behind his chariot’s inability to pass over the place. Nandi informed Ravana that his lord Shiva and Parvati were enjoying dalliance on the mountain and no one was allowed to pass. Ravana mocked Shiva and Nandi. Enraged by the insult to his lord, Nandi cursed Ravana that monkeys would destroy him. In turn, Ravana decided to uproot the mountain Kailash, infuriated by Nandi’s curse and his inability to proceed further. He put all his twenty arms under Kailash and started lifting it. As Kailash began to shake, a terrified Parvati embraced Shiva. However, the omniscient Shiva realized that Ravana was behind the menace and pressed the mountain into place with his big toe, trapping Ravana beneath it. Ravana gave a loud cry in pain. Advised by his ministers, Ravana sang hymns in praise of Shiva for a thousand years. Finally, Shiva not only forgave Ravana but also granted him an invincible sword. Since Ravana cried, he was given the name “Ravana” – one who cried.
Reference and citation.