Although it was extremely hard to decipher the contents of the notes, Aria was able to vaguely get the meaning of it.
It was an experiment aimed to create a chimera from a human and a spirit. Something that was impossible going by the theory of nature in itself.
Take Alena for example. Even entering a contractual relationship with Ilyin had her in shambles just because Ilyin refused to accept her wholeheartedly at first.
Spirits were beings that had a will of their own, and roamed the world freely as they wished. If they did not take a liking to you, then you best bet you can't convince them to aid you in any sort of way. Even worse if they grew to despise you.
Unlike all the other components Aria had mentioned previously, spirits were entities that couldn't be trifled with that easily. They were essentially the building blocks of the world, ones that gave support to the world's affairs.
