This essentially proves he does not WANT to return it to Mystra. It is strong evidence he never planned to, either, but not proof.
However, note that even his neutral path is "I want to see my rivals humbled, jealous of the majesty I have become". This also suggests an aspiration to transcend humanity. All in all, I really do suspect Gale was experimenting with strong magic until it backfired on him
I think that's right - an ambiguity that was never resolved in 3.5 is "are Shadow weave spells capped at level 9 like weave spells or do they go up to level 12 like Mystryl's weave did"
Is the shadow weave the dark reflection of Mystra's weave of Mystryl's weave - if it's the latter then shadow weave is the only way someone at Gale's level - an archmage and a chosen - could gain more power. I think he went looking for the shadow weave and found it but also found out that Shar is a harsh mistress.
