The Manastorm Decision
The Manastorm Decision appears in Hall of the Guardian during 
[10-45] Finding Ebonchill.[65.13, 48.69]
Contents
<most of the book is indecipherable with age>
...and so it was his fate to be cast into the Twisting Nether, never to return to Azeroth. Even his own son, Millhouse, turned on him in the end, though it is my opinion that Millhouse did it for reasons other than the fate of Dalaran and Azeroth.
It is absurd to think that Magnus could ever free himself of the magical wandering prison we crafted, but there is tiny particle of doubt that pervades my thoughts. Still, we had no choice. Magnus had the impossibly rare problem of being more dangerous dead than alive.
<There are a few more legible notes on the creation of something called the Phantasm Zone, a prison dimension within a dimension that could fly through the Twisting Nether forever, its occupant able to see out, but never escape>
Patch changes
Patch 7.0.3 (2016-07-19): Added.