The Lost Shrine of Bundushatur, softback adventure for AD&D 2nd/2.5th edition, by Michael D. Wagner
“Long ago, the Lords of Chaos strove with the forces of Law and were defeated. Their great temple destroyed and their minions scattered to the four winds, the Chaos Lords withdrew, and a new balance held sway in the land. But prophecy said thta one day the fallen temple would rise again, heralding the Lords’ return to spread Chaos across the world once more.
And now comes a cry for help from the dwarves of Isar, saying that the Lost Shrine has risen from beneath the dark waters of the lake that kept it hidden for thirteen centuries. Already forces are gathering—some eager to plunder the temple’s legendary treasure, some wishing to join under the Chaos Lords’ banner, some desperate to destroy the shrine before the world they know is swept away.
“Find the Chaos Key,” says the prophecy. “The hand that holds the Key may shape the future.” But will you be in time to be the one?”