But as it is...
I can suggest the following:
-The Dwarves, together with part of the Elves, launched a rebellion and left to form their own kingdom. However, due to greed, they decided to betray the rebellious Elves.
-The Elves, in turn, formed an alliance with the Swamp Orcs and went to the Dungeon to reclaim territory for their state. In the end, they won and stayed there.
-During a council meeting, one of the mages, after his troops were defeated by a group of skeletons and zombies, suggests using "airspace" to protect themselves temporarily from ground units. At the same time, the Necromancers are oppressed.
-The Orcs simply join other cities and disappear from military operations. And the dissatisfied groups are simply killed by other races.
-The Elementals - it's clear, a rebellion, a revolution, and an inability to create a normal kingdom.
Here are a couple of ideas. I understand that it's not very good, but it needs to be fully developed. Then it would be better. P.S. I can't come up with anything for the Orcs because they are the strangest race.