"What is this place?" Karen stared out over the edge of the cliff. They seemed to be above the clouds, whose grey mass rolled and boiled, just out of reach below them. Further out, there was more of the same. There was no horizon - the horizontal expanse of clouds just joined with the sky, curling upwards into a hazy canopy. The leaves in the trees behind them hung still and silent.
"This is the emptiness. The edge of the world, where everything ends," said Karl.
"Why are we here at all?" asked Kasey, working at a rock in the ground with his toe. The other two ignored him. He got the stone loose, picked it up and attempted to skip it across the clouds. To everyone's surprise, it actually did jump once, twice, then dropped out of sight.
Karl knew why they were here. He decided to try and explain.
"You know our world has been dying. Fires don't burn as bright, the sun is a faded red orb in the sky, the air feels thinner. Yes?"
Karen nodded. Kasey tried to work another stone loose.
"We're adrift," said Karl. "A world without anchor."
"Worlds don't have anchors," Kasey objected.
"It's a metaphor," said Karen, then indicated at Karl to go on. He thanked her with a silent nod.
"Our world is one of many. The wizards used to use strong magic travel between worlds nearby - other healthy, strong worlds - but we aren't one of those any more. The River of Worlds-" Kasy began another interruption, but Karen cut him off with a look. "The River holds us together while we're strong, but when the worlds get weak, they drift away. That's what's happening to us now."
There was silence for a while, and they all contemplated the clouds at the edge of their world. Kasey skipped another stone.
"What's at the end of the river?" asked Karen.
"Logjam," said Karl. "The fading, dying worlds all crammed together tight."
"Edge to edge."
"So right here will be another world, and we can just walk there?"
Karl nodded. They all watched where the horizon should be, imagining it draw just a little bit closer. Kasey pitched another stone and they all watched it skip on the clouds once, twice, three times, four.
Mokalus of Borg
PS - This basic idea is from A Heretic By Degrees by Marie Brennan.
PPS - I've linked to the PodCastle version, because that's where I heard the story first.