About Karsus & The Weave:
Karsus casts Karsus' Avatar and atytempts to steal the Weave from Mystryl. Mystryl gives her life and her divine energy flows into Midnight (know known as Mystra). The weave is destroyed and then reformed after the Time of Troubles with Midnights' ascension to godhood.
Moments after the fall, spellcasting was changed forever. First, Mystra (Mystryl’s replacement) changes the Weave, banning arcanists from accessing 11th- and 12th-level
magic. Arcanists also had to start spending a great deal of time memorizing spells each morning‚ and they were limited to memorizing spells be level. From this point forward‚ arcanists memorize spells as detailed in the Player’s Handbook. She restricts magic use to only those with the aptitude for it‚ essentially stripping cantras from the common people. Mystra also opened up magic so that an arcanist didn’t have to be a specialist in a certain field of study‚ creating generalist arcanists in the process. This‚ Mystra hoped‚ would
convince spellcasters to use magic for the betterment of humankind instead of experimenting to see how much power they could attain for themselves. Within a few years after the fall‚ arcanists became known as wizards.
Priests were not spared the fury of the gods’ wrath either, as their spells became more time consuming to cast. They, likewise, were required to pray for spells each morning and memorize only a certain number of spells for each level. From the fall forward, priests advance and cast spells as detailed in the Player’s Handbook. Quest spells were placed above their reach as well, except under the most special of circumstances.
About the Nether Scrolls:
This set of 50 scrolls was the foundation for magic use by the Netherese, perhaps by all of the sentient races that developed on Faerûn. Some races, like the elves, brought their own magic with them when they migrated to Toril‚ and it’s doubtful that their style of magic use was influenced much by the nether scrolls. But for the Netherese, their ability to use magic and the wisdom contained within the nether scrolls were forever entwined.
It’s unknown who created the nether scrolls. Some believed that they were gifts left by the Creator Races to the humans ofToril. Others believe that they were a gift from Mystryl, the goddess of magic. Other beliefs hold that the nether scrolls are of unworldly origin, perhaps from the outer planes or from some crystal sphere beyond Realmspace.
What was known about the nether scrolls was that they appeared as sheets of gold and platinum. They were covered with magical runes and sigils that shimmered upon their surface, Anyone who saw them immediately knew that they contained magical power and wisdom.
The small size of each scroll belied its content: Magic weaved its way across the surface, turning a quick-reading page of text into a tome that would take months to finish. In addition, there never seemed to be an end to the amount of informationcontained on a single scroll. As one developed in the mystical arts and re-read the scrolls, new passages and spells appeared.
The nether scrolls were immune to all magical effects, including disintegration spells and ther harmful magic. They could be hammered into an unrecognizable mass, however, as was demonstrated a few times in Netheril’s long history. Eventually, the magic of the nether scrolls would recombine lost pieces of itself, but the time required for such a rebirth was long (it’s unknown if it has reformed currently, but the Netherese never saw the scrolls reform themselves).
The nether scrolls were unlike normal scrolls in that their magic wasn’t just sitting there to be read like a normal scroll. Instead, they were to be studied and pored over, the reader searching for new pieces of magical lore. They were unable to be duplicated by any means, and the Netherese kept them asThe scrolls appeared to be divided into five sections of 10 scrolls each. Just like the scrolls themselves, however, this fivepart organization could have disappeared after enough study.
The scrolls appeared to be divided into five sections of 10 scrolls each. Just like the scrolls themselves, however, this fivepart organization could have disappeared after enough study.
Arcanus Fundare
These first scrolls provided the basics of spellcasting, including the use of cantras, spell components, and the various magical schools (such as alteration and invocation, among many others). These schools were the very foundation on which magic use was built, though the Netherese chose to combine them into three categories (Inventive, Mentalism, and Variation).
Magicus Creare
These scrolls detailed the creation of magical items yet hinted at a wide range of possibilities beyond the basic construction of such items. Magical items that became a part of the creator were hinted at, as was the creation of sentient magical items for specific purposes. Most of the scrolls were stolen or destroyed before much work could be done in this area, however.
Maior Creare
The Creation Scrolls, as arcanists quickly referred to them, detailed the process of creating magical constructs, such as golems. More than that, they also taught the elements of creating living wards (artificial items designed to augment an arcanist—a weak example would be something akin to eyes of minute seeing) and sentient wards (items that actually thought for themselves and had the ability to perform actions, such as an extra hand that
would activate a staff to protect itself).
Finally, these scrolls detailed the properties of antimagic as projected by creatures like beholders. It also discussed ways to both create and destroy dead-magic areas.
Planus Mechanicus
Not only did these scrolls detail planar mechanics, explaining how the different planes of existence were related to one another and how magic worked in each plane, they also detailed the process by which to create pocket planes. These scrolls were the ones that Shadow studied over the course of his life, and he was the foremost expert on planes in all of Netheril.
Ars Factum
This final set of the nether scrolls provided the foundation for the actual creation of artifacts from scratch. It was the most difficult to fathom and required extensive knowledge of all other nether scrolls before one could unlock its power. A few arcanists tried anyway, however, and ended up creating the Crown of Horns and the Scepter of the Sorcerer-Kings.
. And they are obviously still there 
