From the Introduction:
In the far reaches of the world, under a lost and lonely hill, lies the sinister Tomb of Horrors. Terrible traps, strange and ferocious monsters, rich and magical treasures, and an evil demilich fill this labyrinthine crypt.
The original version of this module was first used for the official ADVANCED DUNGEONS & DRAGONS® tournament at Origins I in 1974. Next it was published as Dungeon Module S1 in 1981 using the 1st edition rules. The module was later expanded in Return to the Tomb of Horrors in 1998 using the 2nd edition rules. However, the original tomb was never actually updated - it was reprinted as it originally saw print. Now, twenty-one years after its first appearance, the original module is finally being updated to the latest incarnation of the DUNGEONS & DRAGONS® rules (3.5).