Chronicles of the Crystal Wars Windows game

Centuries ago, a magical plague known as the miasma appeared, which began to devour the surface of the world. Unable to restrain this scourge, the inhabitants of the surface used another form of magic to extract from the ground a giant island the size of a continent in order to dwell in the sky, where the miasma could never reach them. Time passed. Through the fires of wars, a kingdom appeared on the flying continent, whose citizens had long forgotten the tragedy of the forced emigration of their ancestors. And everyone now lives as happily as possible in a human society. But it is several years now that the flying continent seems to slowly sink into the Sea of Clouds. And the nightmare of the miasma surfaces again in the collective memory… Now, a hero has to go back to the surface below to find a way to revive the apparatus which allows the flying continent to remain above the clouds.