After posting that post of mine, something seemed familiar so I checked my notes from 2009 (which I wrote for when I would make an RPG one day, since I was planning on becoming a video game programmer).
According to those notes (which are a bit hard to read; I really ought to get a better handwriting)...
Also, this is the translated-to-English version, the original is in Afrikaans.
Source Cards are special cards that can be used to cast spells. Only some can use it, however.
Cards also have an attribute - each card attribute has a different way to, ah, shall I say, 'absorb' the spell on it.
Fire, Earth, Wind, Water, Dark, Light, Poison, Void, Thunder, Blood, Nature and Source are the known attributes.
Inhumans from Earth will absorb the cards to learn these spells, however, unlike other Inhumans.
That's all known information that I know of.
Maybe we ought to have a compendium of Source Cards and Source Spells?
It'd be handy to use if it appears in the RPG... but that'll happen once I know everything else that goes on there.
Everything's so confusing, I'm in a state of confusion...