On the night of the 9th day of the 10-day Karthigai Deepam Festival Lord Chandrasekharar is mounted on the Kailasha (Ravana) Vahana.
Kailasha (Ravana) or Ravananugraha-murti ("form showing favour to Ravana") is a benevolent aspect of Lord Siva who is depicted seated on his abode Mount Kailash with the Goddess Parvati with the rakshasa Ravana below trying to shake the mountain.
The legend recorded in the Ramayana goes like this:
The ten-headed, twenty-armed mighty King Ravana defeated and looted the city of Alaka (which belonged to his step-brother and God of wealth, Lord Kubera). After the victory, Ravana was returning to Lanka in the flying chariot stolen from Kubera, when he spotted a beautiful place which his chariot could not fly over.
Ravana met Shiva's bull-faced dwarf attendant Nandikeshvara and asked the reason for his chariot's inability to pass over the place. Nandi informed Ravana that Siva and Parvati were enjoying dalliance on the mountain and no one was allowed to pass.
Ravana mocked Siva 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. 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, Siva forgave Ravana and granted him an invincible sword. Since Ravana cried, he was given the name "Ravana" – one who cried.
|The Lord on Kailasa (Ravana) Vahana|
|Kailasa Ravana Vahana|
|The crowd watching procession on night of Day Nine|
The Tamil version of the legend narrates that imprisoned under Kailash, Ravana cut off one of his heads and built a veena from it. He used his tendons for the strings and began singing the praises of Siva which pleased the Lord so much that he bestowed a powerful linga to be worshipped by Ravana at Lanka.
|Vahana shows Tamil version with Ravana's head back of Veena|