User blog comment:AquilaeAltair/Ons Theories. First Theory (S3) - The black matter, something that adquired a physical form/@comment-36009152-20190607002141/@comment-38762161-20190616013049

Well, it is a probability that instead of healing him; it was modifying his instics; as Sika Madu expressed in that chapter, he needed to train Yu better in a way he could control himself; which is the reason why I assume that thing can somehow "heal" or more likely transform the rage within the seraph into a more relaxed seraph.

And I kinda think he's been experimenting with Yu for 600 years. I mean, he mentioned he wouldn't enjoy trying the experiment again since it took 600 years to reach a certain phase

Now answering B, I don't think that would be the case; I kind of think Sika Madu, to a certain extend was kicked out of heaven; there's a part in the Bible on which they say the Devil was able to roam freely on Earth before descending to Hell; perhaps Michaela was just trying to send him to hell, who knows.

It'd be interesting though; and yes, I kind of agree with Urd, Rigr and Ashera being the first test subjects.

Even so, what I find still intriguing and something that I can't decipher is that famous "taboo"