All good things pass away.

You are so young, Lyra, too young to understand this, but I shall tell you anyway and you'll understand it later: men pass in front of our eyes like butterflies, creatures of a brief season. We love them; they are brave, proud, beautiful, clever; and they die almost at once. They die so soon that our hearts are continually racked with pain. We bear their children, who are witches if they are female, human if not; and then in the blink of an eye they are gone, felled, slain, lost. Our sons, too. When a little boy is growing, he thinks he is immortal. His mother knows he isn't. Each time becomes more painful, until finally your heart is broken. Perhaps that is when Yambe-Akka comes for you. She is older than the tundra. Perhaps, for her, witches' lives are as brief as men's are to us.

Occasionally they would hear a harsh croak or a splash as some amphibian was disturbed, but the only creature they saw was a toad as big as Will's foot, which could only flop in a pain-filled sideways heave as if it were horribly injured. It lay across the path, trying to move out of the way and looking at them as if it knew they meant to hurt it.
'It would be merciful to kill it,' said Tialys.
'How do you know?' said Lyra. 'It might still like being alive, in spite of everything.'
'If we killed it, we'd be taking it with us,' said Will. 'It wants to stay here. I've killed enough living things. Even a filthy stagnant pool might be better than being dead.'
'But if it's in pain?' said Tialys.
'If it could tell us, we'd know. But since it can't, I'm not going to kill it. That would be considering our feelings rather than the toad's.'
They moved on.

Tirelessly they flew on and on, and tirelessly she kept pace. She felt a fierce joy possessing her, that she could command these immortal presences. And she rejoiced in her blood and flesh, in the rough pine bark she felt next to her skin, in the beat of her heart and the life of all her senses, and in the hunger she was feeling now, and in the presence of her sweet-voiced bluethroat dæmon, and in the earth below her and the lives of every creature, plant and animal both; and she delighted in being of the same substance as them, and in knowing that when she died her flesh would nourish other lives as they had nourished her.

I can’t bear the thought of oblivion, Asriel,” she continued. “Sooner anything than that. I used to think pain would be worse—to be tortured forever—I thought that must be worse . . . But as long as you were conscious, it would be better, wouldn’t it? Better than feeling nothing, just going into the dark, everything going out forever and ever?

This is what’ll happen,” she said, “and it’s true, perfectly true. When you go out of here, all the particles that make you up will loosen and float apart, just like your daemons did. If you’ve seen people dying, you know what that looks like. But your daemons en’t just nothing now; they’re part of everything. All the atoms that were them, they’ve gone into the air and the wind and the trees and the earth and all the living things. They’ll never vanish. They’re just part of everything. And that’s exactly what’ll happen to you, I swear to you, I promise on my honor. You’ll drift apart, it’s true, but you’ll be out in the open, part of everything alive again.