Future Earth: A summary

The year was 2054 A.D. of the old calendar. Humanity had recently forged a connection to the elemental plane of magic and thus introduced a new force of nature into the world. They had prospered for the last couple years until a major country in the west created devastating magic bombs, similar to nuclear bombs but with more varied and lasting effects. And thus in the wake of their hunger for dominance, they had started World War 4. Until one day where it ended. The fallout from the innumerable bomb sites spread very quickly across the land, until the entire surface area - and some underground ones at the various Ground Zero's - was covered in deadly radiation. This forced the survivors to evacuate underground to wait out the effects, leaving their world behind them. This day would live on in the future archives as the Day of Fate. The surface was lost with no one to blame but humanity itself.
After the Day of Fate humanity has held on underground. But milennia of evolution and irradiated genes have left their mark on them. As humanity grew further and further apart into different cities, to the point of not knowing there is intelligent life outside their own home, they steadily split into several new subspecies; some unique, some similar. These include the slender elves, the short but sturdy dwarves, the tiny gnomes and their sister species halflings, the devil-like tieflings, the reptilian Dragonborn and their relatives Lizardfolk, the large and brutish orcs and many more. Humans themselves also changed to the point of becoming a separate subspecies from their terrestrial ancestors: Homo Sapiens Subterra.
But as much as humanity has changed and evolved, the surface above them has done so even more. With no humans to halt or diverge progress or reshape the planet along with tons of magic radiation to fuel evolution, the world looks almost nothing like it used to. When the magic leaked through to the continental crust it split the tectonic plates into smaller parts. Thus the continents have split and moved as well, creating large inland oceans and new mountain ranges dotted across the globe. The wildlife has changed the most though. Thanks to the magic irradiating their genes and therefore offspring, creatures and plants has evolved much more than they otherwise would. In other words, they fairly often undergo mutations. This has led to a bizarre ecosystem. The sun tree that absorbs and releases heat in addition to sunlight has created a humid jungle in the otherwise temperate France, which in turn has led to animals who adapts in accordance to it like the Solar Dimetrodon. But as fearsome as the surface world is, interplanar connections and research show it could be much worse...
This is the world that humans have left behind. Immense creatures like dragons, re-evolved dinosaurs and ginormous purple worms make it incomprehensively dangerous for an unprepared human. But in the european city of Akadence, there are plans to be set in motion. Plans for the now split humanity to regroup and take back their home.