World Event

Players can trigger a secret new quest in Hell-level games. We don't want to spoil the surprise... so, we'll just give you a clue.
Is it a joke?
No, Blizzard Entertainment's not one to trick players into selling a bunch of Stones of Jordan for nothing. Angry players are dangerous, you know. In any case, it will be difficult to get to for any casual Diablo II player, since it requires you to be in Hell difficulty with a bunch of those coveted rings available for sale.
Then, what could it be?
The word (from Blizzard) is that it's a new quest; it could be pretty much anything. "Secret Beat Cain to a Bloody Pulp Level", anyone?
Is it another Secret Cow Level?
No. Animal rights activists protested and that idea was shot down. Just kidding. Still, no.
Is it a new Act?
A world of no.
Will the secret quest show up in the Quest panel?
Signs point to no, since there isn't extra room in the panel; just enough for six quests on the five Act tabs. Perhaps a new tab would show up if the quest is activated. That wouldn't make much sense either, since there isn't extra room for Act tabs.