The Underdark is a subterranean wonderland, a vast and twisted labyrinth where fear reigns. It is the home of horrific monsters that have never seen the light of day. It is here that the dark elf Gromph Baenre, Archmage of Menzoberranzan, casts a foul spell meant to ignite a magical energy that suffuses the Underdark and tears open portals to the demonic Abyss. What steps through surprises even him, and from that moment on, the insanity that pervades the Underdark escalates and threatens to shake the Forgotten Realms to its foundations. Stop the madness before it consumes you! Note for DMs: This adventure is not for the faint of hearted, to run or to play. The module starts with 10 NPCs traveling with the party through the grueling Underdark. This number can grow. The encounters within the book are often incredibly deadly for the characters that would be going through it. This is because the module expects them to run or talk their way through the events, or, in some cases, the module expects them to lose. If your players aren't the kind of party to run, talk, or surrender, do not get this adventure. The module almost requires that you use milestone leveling because the experience provided does not commonly get players to the levels they should be once they get to certain milestones in the story (7th when they leave the underdark, 15th when they face the demon lords.) Good luck and happy questing.
The Amulet of a Demon Prince In a few days, the rising blood moon will reveal the resting-place of the soul amulet of a forgotten demon prince. A dark lord seeks the amulet, and if he finds it ultimate power is within his grasp. Someone must stop him and his diabolical scheme before evil is unleashed! But for the heroes to beat the dark lord to his prize, they must travel through time and conquer demonic foes! A Battle Throughout Time Chaos Rising is a classic dungeon exploration adventure by Jim Collura, it details an ancient and abandoned dwarven citadel where the demon's amulet is hidden and provides unique encounters allowing the players to travel back in time to shape the very future itself! Chaos Rising supports monsters found in the Tome of Horrors. Also available for S&W and 5e.
It's strange that a shrine to a vanished god should still be taking sacrifices. Not everyone forgets a forgotten god. The party explores an old shrine to a demon lord, kept up by a superstitious local.