After the initial terror of the Spellplauge receded, mages discovered that it had changed the way magic worked all across the face of Faerûn.
The most obvious effects were the floating earthmotes that hovered in the sky and the occasional Spellplauge pockets that continue to burn with blue fire. But the changes were deeper than that. Many spells were more difficult to access and now required elaborate rituals. Others became so easy that wizards could cast them at will.
The entire foundation of magic had been altered, and mages now had to re-learn all they knew.