The Fallen Skies
Welcome to your new campaign!
Twelve years ago, you remember standing with friends and family outside the wooden palisades of Saxenford, gazing south towards the skies in awe.
Three great dragons, who had long lorded it over the skies of Norland, had flown south a week earlier. The Grey Skin overlords had marched the bulk of their mercenaries away at the same time, despite increasing rumours of goblins in the north.
Now, as blue-green eldritch lightning crawled across the surface of the Sky Keep of Des’riador and fed into a swirling vortex in the sky, you watched as a mighty sea-green pulse thundered out of the far south.
The Sky Keep, above Sochester, which lay a few days to the south, tilted and turned over in the bizarre eldritch storm. And then, as the entire world reeled in shock, as if the air had been sucked from everyone’s lungs at once, Des’riador plunged towards the earth.
You remember the sense of panic, and excitement as the adults called everyone within the walls of Saxenford. You watched as Alther the Longaxe, captain of the militia, laid out his plan to protect the town.
It was within that first week that the first refugees from Sochester brought word, the Tyranny of the Sky Tyrants was ended! The Crescent League and their allies, fey and foul, had slain the Queen of the Githyanki and destroyed the source of their power. Norland, and all the lands of the known world, were free again to decide their own destiny.
Three days later, the giants came, following in the wake of their goblin hosts…
After that, take a look at your wiki. There is some more helpful info there.