The Krittikā maidens prayed to Lord Siva. Siva blessed them and said, "Since my son was brought up by you, those who pray to Lord Murugan on Karttikai days will obtain all they want."
Narada Rishi performed puja and from the homam a big ram emerged and started killing people. Narada could not do anything about it, so he reported it to Siva and asked him to control the ram.
Veerabahu controlled the ram and presented it to Lord Murugan as his riding vehicle.