Solomon was correct in banishing Sebastian

Sebastian had become a toxic influence, having him around Anne would be a terrible idea and whereas it seems harsh, it's the right thing to do. I know that the game kinda just let you ignore the lore, but mastering unforgivables, especially at 15yo, is definitely not normal and is a dark wizard trait.

Anne ended up cutting him off too for a reason.

Ominis doesn't cut him off and he's sure to suffer for that choice in the future.