Echocoa
Socially inept but trying >-< (she/they)
That sounds pretty reasonable, assuming Kyserias decided to come to their lands himself. And the way I would say it she was already heavily straining things before engaging Cicero, but the resulting fight and the Corrosion magic would be the very heavy straw that sends her past the tipping point.Cicero has lived his life at the mercy of others and since strives for any self-control he can get.That's part of the reason why he took to teaching so well: so he could position himself in such a way that he doesn't have take orders anymore.
Yeah, I imagine Vaimi's mother eventually decided that it would be a more valuable use of her time cutting the head off the snake than endlessly blowing up Kyserias' soldiers. Perhaps she planned to ambush him somewhere with her intimate knowledge of the land, but Cicero detected this and stopped her right before she could because of his skills/race/experience/etc. They had a grand old fight where it basically boiled down to her being the unstoppable force to cicero's immovable object. Eventually he decided he had no choice but to use the Corrosion magic, damaging her mind and being partly responsible for all that happened after?
I also went ahead and made those changes in the backstory based on what you said, and started adding tidbits about the Ior'lyr clan and Holalana, which I'll continue adding to as I think more about those parts of Vaimi's past.