Once it was warm here, she thought, even at this great height. But this world has grown colder, and the pond froze, right down to its base.

The pregnant Cow mewled, "Nothing can live here. This is no place for us."

The Ragged One rumbled deeply. "We should get on."

But all the mammoths were weary and agitated. Icebones could smell blood and milk in the pregnant Cow’s musky scent. Her sisters clustered close around their mother, reluctant to move further. The Bull stomped back and forth, agitated.

"This is foolish," said the mother, with a sharp slap of her trunk on the ground. "Enough. We are cold and tired, and it is hard to breathe. We should not climb further."

The Ragged One regarded them with contempt. She said simply, "Then I will go on alone." And she turned her back and, with trunk held high, stood beneath the shining Sky Trail.

"Wait," Icebones called.

The Ragged One snorted. "Will you make me stop? You are no Matriarch."

Icebones said, "I will come with you. It is not safe for you to go alone. But," she said carefully, "if we do not find the Lost, you will come down with me."

The Ragged One rumbled, hesitating.

Icebones took a step forward, trying to conceal her reluctance to continue this futile climb. The others were watching her somberly.

The Ragged One proceeded up the slope. Icebones followed.

After a few paces Icebones looked back at the others. Already they were diminished to rust-brown specks on the vast, darkling hillside.

They had long risen far above the sounds of life: the rumbling of the mammoths, the call of birds, the rustle of the thin breeze in the sparse grass. Here there was to be heard only the voice of the Mountain itself. Occasionally Icebones would hear a deep, startling crack, a rattle of distant echoes, as rock broke and fell and an avalanche tumbled down some slab of crimson hillside.

The Sky Trail, ignoring the toiling mammoths beneath it, strode on confidently toward the still-hidden summit of the Mountain.

The ground was complex now, covered by many ancient lava flows: this Mountain had spewed out liquid rock over and over. In places the rock flows had bunched into broad terraces, perhaps shaped by some underlying feature in the mighty slope. The walking was a little easier on the terraces, though the steps between them made for a difficult climb, and Icebones did not relish the prospect of the return.

There were many craters, on this shoulder of rock. Some of them were vast pits filled with sharp-edged rubble, while others were dents little larger than the footfalls Icebones might make in a field of mud. Some of the larger craters were filled with hard, level pools of fresh rock, and rivers of frozen rock snaked from one pit to another.

Ice had gathered in scattered pocks in the twisted rock face, black and hard, resistant to the probe of her tusks.

These scattered pockets grew larger until they merged, filling shallow depressions between low ridges. Soon Icebones was forced to walk on ice: hard, ridged, wind-sculpted ice, it creaked under her feet as it compressed.

If anything this was worse than the rock. On this pitted surface there was no food, no liquid water to drink — nothing but the ice, its deep cold ever willing to suck a mammoth’s heat from her. And the air was thinner and colder than ever, and Icebones’s lungs ached unbearably with every step she took.

She heard grunting. The Ragged One was working at a patch of ice with sharp scrapes of her tusks. Her hair, frosted white, stuck out at random angles from her body.

Icebones lumbered up the slope to join her. To her surprise she saw that a tree had grown there. It had a thick trunk that protruded from the ice, and its branches, almost flat against the ice, were laden with a kind of fruit — a black, leathery berry, broad but flaccid, about the size of a mammoth’s foot pad.

She asked, "Is it a willow?" But she knew that no willow could grow on ice.

"Not a willow," the Ragged One said, panting hard. "It is a breathing tree. Help me."

Icebones saw that the Ragged One had been trying to pry some of the broad black fruit out of the ice. Icebones bent to help, lowering her tusks.

One of the fruit popped out of its ice pit, and the Ragged One pulled it to her greedily. Icebones watched curiously as she used her trunk fingers to pull a plug of a hard, shell-like material from the husk of the fruit, and pushed her trunk into a dark, pulp-filled cavity revealed beneath. The fruit quickly collapsed, shriveling as if thrown on a fire, but the Ragged One closed her eyes, her pleasure evident. Then she cast aside the fruit and began to pry loose another.

"Is it good to eat?"

"Just try it," said the Ragged One, not sparing attention from her task.

On her first attempt Icebones punctured the fruit’s skin, and it deflated quickly with a thin wail. But with her second try she got her fruit safely out of the ice. When she plunged her trunk tip into the soft pulpy cavity, she was startled by a gush of thick, warm, moist air. It was unexpected, remarkable, delicious. She closed her mouth and tried to suck all the air into her lungs, but she got a nostrilful of odorless fruit pulp, and sneezed, wasting most of the air.

She found another fruit and tried again.

For a time the two mammoths worked at the tree, side by side.

The Ragged One poked at an empty skin. "The tree breathes in during the day, drawing its warmth from the sun and the rock, and it makes the air thick and wet. And at night the fruit breathes out again. In, out, like a sleeping mammoth — but each fruit takes only one breath a day.

"The breathing tree was the first tree that grew here. That is the legend of my kind. The breathing tree makes the air a little warmer and sweeter, so that grass and bushes and birds and ibexes and we can live here."

This meant nothing to Icebones. A breathing tree? A fruit that could make a dead world live…?

"Your kind? Where are your kind now?"

The Ragged One’s trunk lifted toward Icebones, its mottled skin ugly beneath sparse hair. "Gone. Dead. I am alone. And so are you. I am not like the others. They are all calves of the calves of Silverhair, the last of the mammoths of the Old Steppe."

Icebones stopped dead. "Silverhair?"

"Have you heard of her?"

"She was my mother."

The Ragged One snorted. "You are her calf? She suckled you?"

"Yes!"

"Then where is she?"

"I don’t know," said Icebones miserably. "Far from here."

The Ragged One said slowly, "Listen to me. Silverhair was the mother of all the mammoths of this Sky Steppe. She was the mother of their mothers, and the mother of their mothers before them… and on, back and back. Silverhair has been bones, dust, for a very long time. So how can she have borne you, who are standing here before me? You must have slept in your box of darkness for an age, squat one."

Icebones, bewildered, tried to comprehend all this. Was it possible? Could it really be that she had somehow slept away the generations, as calf grew to mother and Matriarch and fell away into death, over and over — as her mother’s calves grew to a mighty horde that covered this world — while she, daughter of their first ancestor, had stayed young and childless?

"If what you say is true," she said, "you must be a daughter of Silverhair too."

"Not me," said the Ragged One, discarding the emptied husk of the last fruit. And she strode on without explanation.

Icebones felt a deep, unaccountable revulsion toward the Ragged One. But she hurried after her, following the pale shadow of the Sky Trail.

Within a few steps, all the warmth and air she had garnered from the breathing tree had dissipated, and she was exhausted again.