I'm already planning the next adventure I'll write and publish in the DMsguild and I've decided to create an adventure that tells the story of what happened after the end of one of my 4th edition campaigns.
My homebrew setting is divided up into 5 separate Ages that mark great changes, especially in the physical and magical laws that govern the game itself.
In the 3rd Age a group of humans with an affinity for magic sailed the Great Sea and settled on a group of islands that they called Alrualland. Over a thousand years later, a group of elite soldiers from the Elven Isles were sent by the Elven Emperor to retrieve a powerful artefact. Throughout the millennium, a magical disease had spread throughout Alrualland. Those affected banded together and it was this group of Werecrocodiles (Lycans) that defeated the elves.
The people of Alrualland allied themselves with a dwarven kingdom that lived in the world of shadows called the Kingdom of Beldwhig. These dwarves worshipped Lithor, the God of Earth and Undeath. Lithor raised the elves to death knights, vampires, liches, etc and sent them to Alrualland to defeat the Lycans before they took over Alrualland, Beldwhig's allies.
After the Underworld War, the undead took over Alrualland and ruled as lords and ladies. At the end of the Age, most of them set out into the world to find a means to defeat Ithilba and his elemental army that was threatening Daedaloth, the new name given to Alrualland, which also meant "The Land of the Dead". Unfortunately, these lords never made it back to Daedaloth, and Lady Ahnu Suhni, a powerful lich, was forced to move Daedaloth into the world of shadows where Beldwhig was standing by to aid them. Thus ended the 3rd Age.
A group of Shadar'Kai made it to the Theocracy of Daedaloth, a land of genasi in the Shadowfell. The Shadar'Kai were led by the assassin known as Sunder, who set in motion a plan to take over and rebuild the ancient capital of Al'Rual and eventually overthrow the Speaker, the leader of the theocracy.
During the invasion of Al'Rual, Sunder came across a very special and unique type of lich. Liches in the 4th Age worked very differently from liches in the 3rd Age, and thus Ahnu Suhni didn't keep on being a lich across the Ages. Instead, she evolved into a Suel Lich, a mix between a lich and a ghost, mainly because her spirit was trapped after she had moved Daedaloth into the Shadowfell. Having been trapped for hundreds, maybe thousands of years, Ahnu's soul finally grabbed on to the first partially living thing that came close to her, the revenant Sunder.
This entire plot is now the basis for my next adventure, which will tell the story of what happened after Sunder was taken over by Ahnü's soul, and how such a lich, revenant, and the shadar'kai work. I'll place it in the source of my inspiration, Hallalia, which has suffered greatly since the Sundering, which I'm also going to use to create the locations and events in the game.