We played Ravenloft when it first came out (this would probably have been very late 1983, or early 1984). TPK, one of only two our campaign has had in 25 years. Let me tell you how.
As you may know, there are multiple ways in which one can permanently whack Strahd in this module, but only one particular way will work in any particular running of the module. Our DM determined that it was going to be the "Sunsword" method, and the only candidate sword in the party was that belonging to our half-orc fighter/cleric.
After many fights and harrowing experiences, we had lost two party members (including said half-orc). However, we managed to knock Strahd down to 0 hp, at which point he went gaseous and headed for his tomb to regenerate. We gave chase, leaving our two fallen comrades behind. So, the half-orc, and thus the blade of the Sunsword, were not with us when we passed through the doorway where the Sunsword was supposed to reassemble itself!
Anyway, we head into the dungeon level, and discover that there's literally dozens of crypts. So, we start looking around. One party member, a fighter who hoarded magic items (he had *two* rings of Shooting Stars), wandered off by himself. He walked through a doorway that had a Teleport trap on it. This trap transposed this hapless fighter, and a wight that was in a nearby crypt. But, to make matters worse, it only transposed their bodies -- the wight was wearing all the fighter's goodies.
The now-fortified wight starts stalking the party. Our remaining cleric is also a bit separated from the party, sees the wight, and turns it. The wight runs off. The cleric comes up to my character (a magic-user), and says: "I just turned a wight. It went running through that doorway. It'll be back in ten minutes when the turn wears off."
I start planning strategy. (Keep in mind that I never saw the wight, and the cleric neglected to tell me that the wight was wearing our friend's stuff.) I put a Fire Trap on the doorway, then pace off the area that a Fireball, centered on the doorway, will take up. I situate the rest of the party well out of the Fireball's AoE, and wait for the wight to set off the Fire Trap.
Fire Trap goes off (wight misses his save). I Fireball the wight; he misses that save, too. Our DM (a truly evil individual) says the three words I will always remember..."item saving throws." Both rings of Shooting Stars fail their saves, and the DM rules that they blow up, as well as several other incendiary magic items that the wight was carrying. Those explosions are more than enough to crisp us all.
Then, the DM gets even more dramatic. He rules that the explosion was big enough to weaken the castle's foundations (and remember that the castle is on an overhanging cliff). The whole complex collapses, and slides down the cliff. What fun!
Six months later, my girlfriend and I are at GenCon, and we see a guy sitting at the TSR booth. His nametag says, "Tracy Hickman." We stare at him with malice in our eyes, and hiss, "YOU!" He smiles, and says, "let me guess...Ravenloft?"