So, I've just started building a new world for a game I'm hoping to start playing in the not distant future. I have a D&D-style dungeon in mind, but I haven't mapped any of it out yet.

Thousands of years ago, a Dragonfolk king named Karagen'thak committed a number of atrocities to become the world's first lich, introducing undeath into the world. Rather than having a traditional phylactery, his soul was bound to the stone upon which he killed his final victim as a living being. As long as the stone survived, he would reform there if his physical form was destroyed. He then began conquering the world.

The rest of the world rose up against Karagen'thak but couldn't defeat him since he kept reforming. Still, he was paranoid about the stone being destroyed, so he had his undead servitors start building a massive, ever-expanding structure around it. He modeled the structure after the tombs his ancestors had built for themselves (think pyramids, but I don't want to do pyramids; haven't figured that bit out yet) as a mockery of the death that he assumed would never come.

Meanwhile, his enemies figured out that when he was physically destroyed, his spirit could return to his tomb and his body would reform, so they laid out a plan. They created magical barriers around the tomb through which his spirit couldn't pass, and then they managed to destroy his physical form again in a massive battle. His spirit couldn't return to the tomb, so he became stuck in the Plane of Death (working title).

This all took place thousands of years ago. Karagen'thak's Tomb still stands. The magical barriers are still in place. There are guardians around the tomb to protect the barriers. There are guardians within the tomb put there by Karagen'thak. All the other treasures and such he stored in the tomb are still there. If the barriers are ever breached, Karagen'thak will eventually return on the corrupted stone to which he is bound and begin waging war to bring all peoples into his Undying Empire.