The plateau phenomena you refer to originates from the Sprite King Quill, who was sealed away in ancient times. He was betrayed by his children and locked away in another dimension, far away from Deepfathom.
Quill put a curse on the children that sought to take his power and invested all of his hope in his unborn son. The unborn son is now more powerful than his siblings.
Carso, the Hero of Time, is stepping up his efforts to remove the seals on the ancient Sprite King. The Sprite King's servant Ero is also hard at work at the Ecliptic Tower to make this endeavor a success.
That's why the power is running wild.
I believe that the coming of the true Sprite King is near. Mina should abandon her role as spokesperson for the imposter while she can.
(The way that Kasper's eyes burned with fury made you feel that you should try to stop Ero.)
Once the wild power flows calm down, we will have time to deal with what's happening in the east.
Ardenis is apparently forming an army on Heirloom Peninsula to launch an all-out invasion on the west. The target is apparently the Ecliptic Tower in Misty Plateau.
May the Eternal Mother light your way.