One of the legends from the Purana goes that during the churnig of the milky ocean in search for the pot of nectar of immortality, the devas ( deities, semi-gods) and the asuras ( demons) witnessed the surfacing od a pot of poison Hala hala and they were terrified by this event as the poison could have destroyed the entire manifested universe. They swiftly went looking for help to Lord Shiva. He drank the terrible poison to save creation and all living beings. Lord Shiva did not swallow the poison but he kept it in his throat and that caused him to turn blue. From this episode Shiva gets his attribute Nila Kantha that means the one with the blue throat.
Moreover the night when Shiva drank the poison he was suggested to keep awake. The Gods helped him to keep awake by performing dances and playing music.Therefore on Shivaratri devotees observe day and night fast and they perform puja to the Shiva Lingam (male symbol ). They meditate and sing praises to Lord Shiva.
How do we relate to such picturesque legend and celebration in our western culture and context? If we find the key to interpret the legend we can surely refer to it.
The churning of the ocean has been associated with the internal stirring that is caused by working on opening the spiritual spine Sushumna nadi , the central channel, through the physical and spiritual practices of Yoga . The spine is opened from the base up towards the crown of the head. The milky ocean represents the reservoir of energy at the base of the spine, energy of oceanic proportion. From that churning both amrita ( nectar ) and hala hala ( poison ) emerge. What to do with that poisonous stuff that comes up? Shiva – the accomplished yogi and Lord of Transmutation- indicates that the poison cannot and should not be dispersed or dumped outside our body. It should be transformed and recycled inside Vishudda , the throat centre ( which means the Purifier) and that circulated back into our system. As a result we will be transformed ( change colour) . Last bit of the symbolism is maybe may favourite part: the night vigil Jagran. Avoiding to sleep ( loss of awareness ) seems to be the antidote to the terrible poison. So with the legend Lord Shiva tells us that those who can maintain an uninterrupted stream awareness can survive and defeat their own inner poison!