Fun times for those who started their AQ Sceptor quest, but never finished it. The very last step of the Green Shard questline has you summon Eranikus in Moonglade, then tank him to 20% before he is "cleansed". I was on this step a week or two ago, and after some 3 man farming for my remaining shards (we raiders get bored at 4 am!) I had all of the pieces to turn in. Cue Eranikus, Tyrant of the Dream.
However, before he lands, Eranikus unleashes a MASSIVE number of shadow monsters all over the town. They have a lot of HP, fear auras, AOE shadow bolts, and will require a fairly large number of people (even 70s) working together to kill off.
I'm talking complete and total genocide if there isn't a 20+ raid of 70s who are ready for it. During the moonglade festival, I can guarantee you a good 90% kill to escape ratio. And this event does NOT end quickly.
The best part is, all you have to do is drop the quest, talk to the quest giver (also in moonglade) and restart it. After a short (30-45 second) escort, the process repeats ad naseum. As long as you don't get Eranikus to 20% and turn the quest in you can do it as much as you like.
I did this for a while on Burning Blade US this week, before finally turning in the quest for my AQ Sceptor (which I of course can't use anymore, but not many people have em)
YES I KNOW, not many people have access to this questline, but many old raiding guilds run "legacy" instances (MC, BWL, AQ, Naxx) for fun, and there is lots of opportunity to get this quest.