Quote Originally Posted by Wolfandre View Post
It could be that one doesn't really need a focus to use magic, it just helps (stat bonuses). Therefore, really anything could be used to focus it, including man-made weapons.
I've actually thought about this quite a bit. My end conclusion is that you need a focus in order to cast most of your spells. Think about the spells you get access to through cross-class abilities and they're actually pretty simple stuff: Cure, Aero, Protect, Blizzard II, Ruin. These are spells that could be dirt simple and easy to pull off without any kind of special focus. However, if you wanted to cast the more complex or powerful spells like Shadowflare, Medica II, and Thunder III, then you need a legitimate focus. And if you wanted to cast some really powerful spells, like Tri-Disaster, Sacred Soil, Holy, and Flare you'd need the power and knowledge granted by soul crystals, on top of the normal focus.