An ancient hourglass with fine powdered snow flowing in it.
Even the coldest winter cannot freeze the flow of time.

"The cold that descends from the sky can freeze time itself."
This myth was widely believed throughout the entombed mountain city.

As the hero reached the top of the wall of wind and ice, the night was descending and the snowstorm was howling.
Neither sun- nor moon-light could pierce this white wind easily.
Even the bleakest storm cannot freeze the river of time.

That will not wilt even if buried deep below the snow.
And even the most formidable hero will one day be forgotten.