Well, Risen's guild website is back up after the beating it recieved when they crafted the worldfirst of Atiesh, and it appears this new Legendary staff is even cooler than previously thought. Not only does it have some crazy stats worth of a Legendary item, and not only can it open a portal directly to the previously unseen zone of Karazhan, but apparently this thing even spawns Legendary items of its own.
Paladinsucks has a picture of a sword called Andonisus, Reaper of Souls, which is supposedly a brand new Legendary mainhand sword that makes Thunderfury look like a pointy piece of metal. But there's a catch-- the sword is supposed to be a conjured item (via a usage of Atiesh) that only works in Stratholme, and only for 10 minutes (or 15? or until logout?). Risen's forum has lots of people asking about Andonisus, but not a lot of answers-- one post suggests it can only be spawned during one boss fight, and another forum says it only spawns for the server first of Atiesh.
Sounds awesome, but it would be great to have some solid information on this one. Anyone from Risen want to give us the dirt? Send us a tip on the sidebar and I'll update as we hear about it.
Update: Unfortunately, from what we're hearing in the comments, Andonisus only shows up during a specially summoned boss in Stratholme that you only fight during the crafting of Atiesh. And then, it only hangs around for ten minutes. Pretty limited usage, so don't bother working this one into any of your gear builds. But it is still sweet.