If I had to guess at the latter question, I'd say the purpose would be something like having us be more receptive to the idea of relying on our partners. Since this world seems dead set on matching us up, logically it follows that it'd be insistent on having us work with them.

[Shaking his head slightly, Waver considered the situation before trying to explain things clearly.]

But going back to the 'how', I just don't understand that. I don't think it's really magic--at least it isn't magic as we know it. Given everything I've seen so far, if it was magic in our world's terms we'd be dealing with power on a level no amount of skilled magi or miracles could put forth. Second Magic, probably Third in a very loosely-defined sense regarding summoning rituals...Even if this world isn't fully organic, I just don't think it's possible in any sense.