What's the scariest MMO quest you've ever experienced?

I'm going to go out on a limb here and suppose that you've played a lot of MMOs. You're reading Massively, after all, and since we're something of a specialist site, well, there you go. Since you've played a lot of MMOs, I'm also betting that you've done your fair share of quests.

Some of these quests were probably boring. Some might have been well-written or mechanically novel. And some might even have been scary. Since it's Halloween and stuff, why don't we get into the spirit by reminiscing about scary MMO quests. What's the scariest quest you can recall?

TH