Decline

The last game of the Seasons quadrilogy will be Autumn, even though the story will not be set in Autumn.

Civilization has grown ancient the rulers believe that humanity has achieved enlightenment. Calling modern society "The Ascendant", humans believe that they have reached absolute perfection, but underneath the surface, there is a terrifying truth the rulers of the The Ascendant wish to keep hidden: that all life on Earth has begun to wither and die. They struggle out of sight to prevent the inevitable extinction of all animal life while maintaining to the public that all is well; they have achieved enlightenment and will live on in eternal bliss.

However, human technology has advanced so far, they have created a new lifeform. Made in the image of their creators, Simulants are gentle, curious creatures, and they are completely unaffected by the apparent plague destroying all life, leading some to speculate that they could be humanity's salvation...

...And others to speculate that they could be the cause.