tome of unused magic

The tome of unused magic is a unique magic item written by a long forgotten Nethen researcher searching for ways to discepate excess magic created by the early Karenthian Batteries.   The Nethen researcher studied the laws of planes and planer research, and found that for every source of magic, there was an opposite source or devourer. The researcher compiled the knowledge and created a ritual to use to open a portal to send excess magic to. The problem is that the created portal sucked all the surrounding magic into itself, including all the magic within the researcher, killing him, and absorbing much of the surrounding magics of the city over time. But an open portal from one dimension to another is an invitation to both sides. Creatures from the anti magic dimension sensed the feast on the other side of the portal and swarmed into Plane of Karenth. Battles raged throughout the city. Nethen died everywhere as their magics were useless, and they were forced to rely on few normal items they had laying around, including shovels and pitchforks.   Eventually the Nethen Council and military got to the portal and were able to close it. By this time tens of thousands of anti magic creatures swarmed through the lands, eating magic, killing living creatures, and spawning new creatures.   Once the portal was contained, it and the book were taken deep into the vaults of the Nethen and buried away. However the swarms of creatures continued to ravage the lands and non Nethens and Nethens alike fought the creatures. Eventually, the battle was going bad and the Nethens sent much of the normal population through what is now Freedom's Gate to the world of Els'tar, leaving themselves behind.   Shortly after this, the Nethen found a way to taint the magics preferred by the hord and poisoned most of them bringing the issue to an end.