Prisons of Ice and Fire

A CliFi short story.

Imagine a place where there is a searing thousand mile desert that runs to a sea...
...a sea that one hundred miles off shore is so cold you die within a minute if you fall in.
Five hundred miles to the south of the sea is a frozen landscape in perpetual winter...
... a place that is always snowed on and that frequently calves monster icebergs.

Hardly anywhere on land is safe; little life survives.
The last refuge of mankind are the Stilt Cities, floating in the middle of the ocean.

To the north are the Desert Domes: the last farms, protecting plants from the intense heat and sand.
To the south the Ice Quarries: the last supply of fresh, cooling water.

A current system moves strongly along the divide of heat and cold, but rarely over it.
You, however, move across it like a metronome... tick... tick... tick...

...and as the prison ship Destiny plies the waves, a secretive cult have a strange request of the Captain.