Heart's tale

A long time ago, there was a planet on the surface of which a real living Heart was beating. Each of its beat gave life to many wonderful creatures, and humans were no exception.
Once, during a mountain collapse, they became afraid that something might happen to the Heart, and built a fence around it. And they started arguing about who is the worthiest defender of the Heart. The fence turned into a wall, and the city rose very quickly around it. Everything that people came up with was immediately brought to life by the love of the Heart. So, they created dolls to help themselves, which significantly accelerated the construction. In the time that was freed up, people took up the war.
One day they closed the Heart completely, erecting a dome over it. Miracles stopped happening, and the dolls stopped coming to life. People blamed magical creatures for this and began hunting them. And in order not to stop the construction, they began to chip off pieces of the Heart and insert them into their mechanisms. The city continued to grow.
Centuries have passed. The city has propped up the sky with towers. Only fragments of the Heart remained, saturating the black smoke with its breath. Factories that produce nightmarish monsters fed on it. With their help, people continue to wage war with each other for the title of the worthiest defender of the Heart. While it is dying. This is where our story begins...

This is a translation in process. So I am open for suggestions and comments on what to improve in the flow of the text.