The Ocean of Milk was being churned for nectar.
That was the prize that had brought gods and asuras into the same enormous task. Mount Mandara served as the churning rod and the serpent Vāsuki as the rope. Even getting the work started required help, because the mountain sank and had to be supported before the churning could continue.
Then the ocean began to give up what was hidden inside it.
The first great thing to emerge was not nectar.
It was poison.
The Bhāgavata calls it hālāhala. The chapter describes the ocean in turmoil and says the poison spread forcefully in every direction. This was not a vessel someone could put a lid on. The danger escaped the project that had produced it and threatened living beings who had never agreed to churn anything.
The gods and other leaders became afraid and went to Śiva, who was sitting with Bhavānī. The chapter has already shown fish, sharks, tortoises, snakes and enormous creatures in the ocean thrown into confusion by the churning; now the poison makes the disturbance a danger to the wider world.
They asked for protection.
Śiva did not pretend the poison was harmless, and he did not speak as though the danger belonged only to the people who had caused it. The text has him turn to Bhavānī and point directly at the living beings now suffering because the poison is spreading.
He says that those who have power have a duty to protect those in distress, even when protection carries risk for themselves. He frames the act as protection of dependents and as service pleasing to the Lord, not as a contest to prove that poison cannot hurt him.
Then he tells her what he intends to do.
Bhavānī knows his power and gives her consent.
Śiva gathers the poison into his palm and drinks it. The verse names compassion for living beings as the reason for the act. It is explicit that he takes the whole quantity into his palm, not only a portion of it.
Bhavānī has already given her consent because she knows Śiva's power. She does not need to take the act away from him: Śiva gathers the whole quantity into his palm and drinks it himself.
The poison leaves a blue mark on his neck.
The chapter immediately changes the meaning of that mark. Something that shows the force of the poison becomes an ornament because of the reason Śiva accepted it. The text says gods and people alike praise the deed after they hear what he has done.
A small amount spills from his hand while he drinks. That detail is unusually concrete after such a cosmic crisis: even the remnant is not treated as harmless. The text connects that remainder with scorpions, cobras, poisonous plants and other creatures whose bite or substance carries poison.
Only after the poison has been contained can the churning continue toward the nectar everyone came to seek.
The work did not immediately reward the people doing it. It produced a crisis first.
And the person who absorbs that crisis is not taking the nectar for himself afterward. Śiva's role in this chapter is to make it possible for everyone else to continue.
The blue neck remains after the danger has passed. Helping has left a visible sign.
Śiva does not drink hālāhala and emerge looking untouched. His neck carries the colour of what he took in.
Śiva does not accept the danger because he has nothing to lose. He accepts it because living beings are in distress and he has unusual power to protect them.
Only then can the search for nectar resume, after the danger that nobody came seeking has been carried by someone who chose to protect the rest.
Everyone came to the ocean for nectar; before anyone could receive it, Śiva took into himself the thing that could have ended the whole attempt.