[@Raylah]Due to the toxins (most likely something otherworldly and not known to earth) that were released when the worldwide fire occurred, mutations and things of that sort happened almost instantaneously to those that were in direct contact with said toxins. (Primfira and Exodus.) What caused the explosions and fire is still unknown, most likely some sort of bomb dropped. The reason we are so many years after would be because the world was nearly inhabitabal for a lot of those years. Many of each race dying off, those who were able to survive being the ones who would repopulate each race. Some areas were less polluted than others toxin wise, making mutations rarer in the other kingdoms. The oldest elders that were alive during the time of the fires would have mostly died off by now, but they would definitely have explained briefly what the world was like before the fires. However, having little people and resources, there was no way to get back to that way of living. At least not anytime soon. 

There most definitely would be remains of buildings, no belongings because those would have been turned to ash. However these remains would be located outside the area anyone travels. Sand too thick to even see what’s left, dangerous sandstorms with razor sharp blades of crystallized sand in them, and who knows what else. 

The kingdoms are on the only area on earth capable of being inhabited. This part is where the elders found to be the safest, taking the least amount of damage and with time and work it became green once more. With Primfira’s smarts and Earthica’s green thumb, they would have created the liquid that helped speed the process of growth in the plants/land. (The liquid Earthica would later keep for themselves as the races broke apart into kingdoms.) 

As for the Exodus king, that’s fine. I think someone was willing to play that role but if not, you can definitely make it a NPC.