I have a group that got tpk'd while playing The Cult of the Reptile God, and they were captured and brought to Explicitica Defilius. Everyone loved the npcs, their characters, but we only got to around level 3.

Flash forward a bit, we are now playing in Skyrim, and the "Bbeg" is the dragon born, a vampire lord with the blood of dragons who dominated the country.

I had the idea of tying the campaigns together, perhaps ED consumed them and discovered an Elder Scroll that had somehow gotten into Greyhawk. She then used it to merge the two worlds OR reincarnated herself and the previous characters into the dragon born (or someone else in the world)

I know this is a bad idea when done wrong and will feel very forced. I just kind of want to make their previous characters important in some way to this world.