[Update]: After a successful beta, World of Warcraft Classic's fresh servers are coming this November 16 with the Season of Mastery.
Out of all the events throughout all of World of Warcraft, the original opening of the Gates of Ahn'Qiraj is probably the most memorable. Not only did it require the combined efforts of an entire server in order to kickstart the invasion, but it also brought in two highly mysterious and long-awaited raids.
While the mystery is sadly long gone at this point, what with us knowing everything including C'thun's favorite brand of eyeliner, you can at least experience a bit of that oldschool excitement now! In other words, as a part of the latest World of Warcraft: Classic update, the Ahn'Qiraj event has just returned in all of its glory!
Expect to see an incredibly lengthy quest chain to craft a Scepter of the Shifting Sands that rewards a one-of-a-kind Qiraji mount, a brand new end-game reputation to worry about, as well as a large-scale war effort that will require the entire server to gather an assortment of crafting materials. Once all of the materials have been collected and the gong successfully bonked, the two raids will become available after a rather monumental (and very likely monumentally laggy) struggle!
You can read a little bit more about these events, as well as which materials are required from each faction, over at the WoW: Classic website. Have fun, Ahn'Qiraj's quite an interesting place!