Well, let's see...
This wouldn't be too hard. I'll start off.
"Highpoint, and the titular continent, was the usual fantasy world until a hundred years ago. That's when the moon, for some reason, shifted closer to the planet, bringing a nightly rain of burning particles that could be the size of sand or the size of buildings. The lunar rains also brought the terrible lunar creatures, including the titanic Lunar Dragons. The surface of Highpoint has never been the same since this catastrophe began.
Most of the surface dwellers tried to flee underground, overrunning some of the weaker dwarven strongholds and causing a lot of ugly incidents. Everyone was in bind until the largest dwarven city was visited by an old dwarf who claimed to know a way to fight back against the giant lunar monsters. He instructed the people in building the first mech, and it was able to score a victory against a lunar dragon. The old dwarf taught some people in the applications of steam technology, and left, though his three assistants stayed to oversee things and teach more people.
Now, almost a hundred years later, the dwarves are the dominant force. Their five huge city-mechs, each home to thousands of people, patrol a huge stretch of land in the central continent, and smaller mechs are commonly used for transport and combat, and the technology has spread. The formerly nomadic humans have organized behind a charismatic leader and have two city-mechs of their own which control and area to the south-east (I think. I'd have to look at the map and I'm too lazy to go for the book.). The elves in their ruined northern forests have developed their own brand of mech-making, and have devoted all their resources to trying to preserve their heritage and culture."