[quote=@Rizza]
<Snipped quote by Prisk>

Thank you for this, I may have been looking at spirits the wrong way; i believe i understand now. I was thinking 1 spirit, alone, would unlock a specific magic type. The user would then gain access to more skills within that "magical tree", with time and experience. Though, if I'm understanding this correctly, spirits are much like materia in the sense that they are linked to a single ability. So, they may make you stronger, faster, grant you a magical attack, etc. but it will only be one of these.

Sound about right?
[/quote]

I've always left how it actually works rather vague. It's a matter for scientific study within the world itself. I had a player once who delved into this stuff through secondary characters. The connection between spirit possession and exertion of magic is unknown. It might be the combination of several factors. However, a single spirit or a even a couple won't do anything. Most people in the world are possessed by a spirit or two. It's the density of spirits that matters. Spirits also merge with each other. I tried to explain it all one time with some help from players, but it became so complex that I just left it vague instead.

Think like this: If you have a tiny lump of clay, you won't be able to create much. But, if you have an entire beach of it, you'll be able to create wonders. The clay is spirits.