Q: How come it requires ToB? Is it some scripting or spells or wild mages or something?
A: First of all, some scripts in the mod use *SpellRES actions. Although you can technically use them with just SoA by adding them to your action.ids, we decided to play on the safe side. I think along the way there was also some other reason for requiring ToB (I think it might have been a ToB spell that I used somewhere), but I cannot remember it right now. At some point, when I go through everything once more, I might check whether we ended up using something ToB-specific or whether we could just have the mod append the missing SpellRES actions to action.ids (if they are not there already) and have it work without ToB. But for now, I *think* you will need ToB.
All right, I looked into the ToB issue and found out that we use ToB only action MakeGlobal() in our area script, and I don't think that I want to go back fiddling with those - not now at least... Areas have caused enough stress as it is.
So, Amber will require ToB. Sorry about that, all you who never got around buying ToB.