The white seaweed lay in the water of the canteen, as long as his hand, and it glowed.
Its light was softer than the gold of the walls, softer even than the room where the needlefish had changed, like moonlight on snow. There was no green left in it anywhere. Even its smallest roots were white.
Mav reached for its point in his head.
He knew every seaweed that he had ever owned by its point. Each one was a little different, but they all felt the same underneath: hungry, patient and close to One, like small cousins of the thing around his chest. This one didn’t feel like that at all. There was no hunger in it. When he touched its point, it felt warm and slow, like a hand laid on a fever.
He looked at the water mover. Her breathing had grown faster. The wet sound under each breath was louder than before, and under his hand, the gray root had almost reached her neck.
"What is it?" Sela asked.
"I don’t know."
He wanted to give her a better answer, but he told her the truth, because there was no time for anything else. He didn’t know what a white seaweed was, or what it did. He only knew one rule, the oldest rule that he had, the one that he had learned in his first week in this World. One seaweed, one host.
The water mover already had a seaweed. It was wrapped twice around her neck, green and alive, fighting the gray thing as hard as it could. If he laid a second one on her, the two of them might fight over her. He had no idea what that would do to her body.
"Will it take her?" Sela asked.
"It might. Or the two of them might fight inside her." Mav made himself say it plainly. "I don’t know, Sela. It could kill her."
Sela looked down at the water mover’s face. The young Reefkin’s eyes had closed again. This time, they didn’t open.
"She’s dying," Sela said. Her voice shook. "Do it."
-----
He didn’t put it on her neck.
He didn’t want it to take her, if it could take anything at all. So he laid the white seaweed on her chest, over the place where the gray root had gone in, as gently as he could.
For a moment, nothing happened. Mav was terrified that he had just killed her.
But then the seaweed moved. It didn’t push its roots into her skin, the way that every seaweed that he had ever owned had done. It spread. Its roots opened across her chest like frost spreading over glass, thin and white, until it covered the broken place from one side to the other. Then its glow grew brighter.
Under the white frost, Mav saw a thin gray line in her skin, running up toward her neck. As he watched, it went pale, then white, then nothing at all. The white seaweed was following the gray root through her, all the way up, and eating it as it went.
The water mover gasped once, loud and short. Mav felt her own Regeneration come back, all at once, like a fist opening. Then he heard the bones move, with a soft sound under the skin, like ice settling on a pond. Her breathing changed. The wet sound grew fainter with each breath, then fainter still, and then it stopped.
Her eyes opened.
Her own seaweed had done the rest. Its Regeneration had only needed that gray thing out of the way. In the time that it took Mav to understand what he was seeing, her chest was whole.
Then the white seaweed let go.
It drew its roots back from her skin, slowly, the way that a cat draws in its claws. It curled up into a small, pale knot on her chest, and it lay still. Its glow had dimmed. When Mav reached for its point, he felt it there, tired, but alive.
It had taken nothing from her. It hadn’t even tried.
[Seaweed. Rank F+. Host: none.]
[This seaweed has changed. It eats whatever doesn’t belong in the one who carries it. It never takes control.]
Mav read the lines once, slowly. Then he picked up the small white knot with two fingers and put it back into its canteen, as carefully as if it were made of glass. He closed the lid. His hands weren’t steady.
-----
The water mover sat up.
She looked down at her own chest, then up at Sela. She put her small hand flat where the bone had been broken, as if she didn’t believe it. Then she sent Mav a picture, quick and bright, of herself standing on her feet.
Sela was crying with relief.
Mav had never seen Reefkin cry. He hadn’t known that they could. The tears ran out of her large dark eyes and down her gray cheeks, and she didn’t wipe them away. She held the young water mover’s face in both hands for a moment.
Then she let go and scolded her.
"I told you to stay behind me," Sela said. "I told you in the first ring, and the second, and the third. You don’t listen. None of them ever listen." She sniffed. "Next time, I’ll put you in a canteen."
The water mover sent a picture to Mav of herself inside a canteen, very small and unhappy. Mav laughed out loud. It came out cracked and strange, after everything, but it was a real laugh, and it felt good.
Pip and Puddle had watched all of it from the shaft, side by side. Pip asked whether the white seaweed could make their young grow bigger. Puddle told him not to be greedy before Mav could answer, and Pip sulked for the rest of the hour.
-----
They rested at the edge of the shaft after that.
The others slept. Mav didn’t. He sat with his back against the gold wall and the canteens in his lap, and he thought about what had just happened.
A seaweed that cleaned, and took nothing.
He thought about the gray threads of this place, moving dead crabs like toys. He thought about the smiling raider at the Tangle, and the black threads that had made One go tight around his chest. Someone in this sea, long ago, had grown something to fight things like that.
With one of these in his pocket, could any thread ever take one of his again?
Nobody could say yet. But it was a gift, maybe the greatest that he had found since the anchor. He was so grateful for it that he didn’t know what to do with the feeling. He didn’t know who to thank, so he thanked the ruin, in his head, quietly, a little foolishly.
A worry came behind the gratitude, slowly.
These were his free seaweeds. They were the seaweeds that he would raise for his next strong host, or lay on his best young, or give to the Reefkin who asked for them. A green seaweed took a beast and held it. That was what made his army. If they all turned white down here, he would go home with white seaweeds, but with nothing to take a single new host.
He looked down at his own chest, at One.
Under his shirt, it lay wrapped twice around him, as green as it had always been. Nothing about it had changed. He felt it move very slightly against his skin, as if it knew what he was thinking and wanted him to stop.
Then he opened the other three canteens again, one after another.
The pale seaweeds inside lay still in the water. They were paler than an hour ago, much paler. One of them had a white edge along its leaves now, thin and bright, like the first frost on a window.
The other canteens were turning white too.