Wow! I can't believe it's a nodeshell!

Tomb of Horrors is a Dungeons and Dragons adventure module published in 1978 and written by Gary Gygax, the creator of Dungeon and Dragons.

This is, quite simply, one of the most brutal dungeons ever published. Never enter it with a character you plan on keeping.

It is light on combat and heavy on deathtraps, including spheres of annihilation, pit falls, and chests filled with deadly gases. Players need to be extremely bright, creative, and lucky to survive the experience.

Oh, and then there's the demilich at the end...

In 1998, TSR released Return to the Tomb of Horrors which builds a greater campaign around the original tomb and features even more deadliness, though mostly in the form of deadly monsters and demons. PCs that reach the end of this epic story will be faced with the true form of Acererak and will need to stop him from achieving godhood.

Synopsis from the Return to the Tomb of Horrors box set:

Imagine a place of unspeakable evil. It was built upon hopelessness and filled with unending terror and pain. This loathsome place shattered the life of everything who ventured near. But through tremendous sacrifice and heroism, over the course of many years, it was finally gutted and its foul creator destroyed.

Now imagine that the horror is beginning all over again.

The sinister wizard Acererak took great pains to safeguard his tomb. It took many years, and many more lives, before his evil was finally laid to rest. But though the demilich is gone, he is not forgotten. Others who would become as he was have travelled to the site of Acererak's tomb seeking the secrets of mastery over death. Slowly these pilgrims gathered, eventually building in the shadow of the tomb itself a community dedicated to the dark arts: Skull City.

But even these twisted necromancers have no inkling of the true evil that swells and crackles beneath their feet.