After Karsus entered the mage Tower for his seclusion ...
Garen knew that everything was on the right track. All these years, he and the goddess of magic had been pouring the framework concept of the godly Ascension technique into Karsus, intentionally or otherwise.
Although it wasn't directly stated, it was enough to plant a seed in Karsus's heart.
For Karsus, he knew that the power that could destroy all the Filin sunflower in one go could not be found in the main material world. It could only be the power of the gods.
Arcanists, on the other hand, did not believe in gods.
He would not ask the gods for help.
Karsus wanted the power of a God to save Netheril. For this, he needed the spell of Ascension, which was launched with a God as the target, in order to seize all the power of a God.
Now, it was time to wait for the day he ended his closed-door cultivation.