I don't think any rulebooks spell it out in much exacting detail as you are seeking and mystra was dead before the first 5e rulebook was written. Aside from being goddess of magic, she was also the lady of mysteries .... which could explain why the answers you seek are shrouded. Finally the weave is specific to the forgotten realms, while the 5e rulebooks encompass many wolds so forgotten realms lore would not necessarily apply in the rulebooks.
Mystra tended the weave but she did not create it. It would have been created before she became goddess of magic, perhaps by Mystryl (her predecessor) or perhaps before Mystryl even.
The concept of slots is new to 5e so it is not correct to say this mechanic was implemented by Mystra as it did not exist while she was still alive. She did control aspects of the rules of magic but, not all of it and they changed after she with magic becoming less rigid and more chaotic due to the changes in the weave.
Here is what I know: The weave was "frayed" (that term actually being used in novels) when Mystra died the second time and that fundamentally changed the way magic is used. This brought about sorcerers. Sorcerers access magic different than wizards in that they useg an inate feel and instinct for magic that was only possible after the weave frayed. Wizards use discipline and methodical study. It is possible slots are a fallout of that, although a delayed one since it was not present initially. The death of Mystra affected wizards the most and initially their spells were completely uncontrollable, over time they learned to master the frayed weave. Over time the weave itself also became more stable than it was immediately following Mystra's death, due to Elminster and others anchoring it to ancient Mythals. Clerics were also affected by the weave tearing but not as much as wizards were.
Last edited by auburn2; 29/12/20 06:42 PM.
