Mmm, gurl, u kno ha I liek me sum xpozisun.
I like it so much I wrote a chapter summary
I guess the first thing that was revealed was how Yhwach's power worked. He gives a portion of his soul out to others when they touch, but only just enough to complete their own soul. He gives people what they lack on their own, but what they believe they need to be better. Notice that the examples given were curing disease, mending a broken heart, bestowing courage, or returning bodily function to someone. What of a paraplegic man whose heart was broken because his wife left him, saying he was too small a cowardly for her? What does this man get if he laid a hand on Yhwach?
Yhwach patches their souls in a very specific way that allows them to become whole persons. He gives them what they need to become actualized people. The comment about those people not lasting long could be a hint of some trickery on Yhwach's part. Besides his ability to give powers, we don't know exactly how much control Yhwach or the person receiving the power has over the process. It would seem the recipient is because it shouldn't be possible for Yhwach, as a newborn baby, to be able to give others exactly what they needed to complete themselves.
Yhwach's power seems like the opposite of what the Hogyoku does. They each improve a person and strengthen their souls, but the Hogyoku does this by creating situations and opportunities for the person to better themselves and increase their own power. Yhwach does this by just giving them exactly what they need/want without any of the experience, training, or maturity gained when they go through the Hogyoku's process. Which makes me wonder whether the people that died after receiving Yhwach's power did so because of their own stupidity or because Yhwach Selected them and took his power back.
Next is the way Yhwach spoke when the portion of his soul James held returned to him. He openly spoke and communicated with it, rather than just instantly gaining the knowledge it held. I would guess that each portion of his soul that is lent out becomes just like Ichigo's inner spirit. An alternate version of Yhwach that wears giant sunglasses and a black jacket. Besides that, Yhwach actually told this piece of his soul to return. If he had to tell it to do that, that means that there was another course of action it could have taken rather than just returning to Yhwach. What else could it have done? That may or may not become relevant in the future.
The interaction between Uryu and Haschwald reiterated that Uryu was supposed to be Yhwach's successor and share his power. Which was strange at first, but made even more questionable after learning what Yhwach's power actually is. It just deepens all of the mystery around the subject.
Though, I like how Haschwald got angry when Uryu made that horrified face after learning Yhwach had written on his soul. Did Yhwach even tell him he was drinking blood?
Yhwach's power is described as the opposite of all other Quincy's power. Rather than absorbing reishi (which has its own soul) he instead gives part of his own soul. This is another slight hint about Yhwach and Quincy because it reveals that, even when having a power that is opposite to all other Quincy's power, Yhwach is still a Quincy. That just tells us that the determination of whether or not someone is a Quincy has nothing to do with how their power works. Unless we want to define them as having the power to transfer of souls, but even then that seems similar, if not exactly the same, as what Shinigami and Fullbringers should be able to do.
The big reveal of this chapter was to learn that Yhwach was not only amassing power from the Quincy that died, but also from the Shinigami that died during the battle. Yhwach became more powerful whether he won or lost. Could this be why Soken really wanted to stop all of the fighting between Quincy and Shinigami? Because it was such a cash cow for Yhwach to have his Quincy and the Shinigami constantly fighting each other?
There's the small question of how Yhwach managed to get parts of his soul inside all of the Shinigami. Maybe it also happens when someone comes into contact with a person who is holding a portion of Yhawch's soul? They become infected by proxy.
A very important note is that, while talking to Uryu about the fate of people who hold a piece of Yhwach's soul, Haschwald has the exact same pained look in his eyes that Uryu does. That look basically gives away his whole character. Uryu will try to take down Yhwach, and he will have help on the inside.
This is my own theory, but before Yhwach notices, Uryu must awaken his Schrift and use it to give parts of his own soul to all of the Stern Ritter and everyone who holds a part of Yhwach's soul. Then, when Yhwach finds out, he wont be able to kill them with his Selection because they will also have Uryu's soul to survive on. Then, even if Yhwach takes his A ability back from Uryu, which may not be possible, Uryu and everyone else will survive.
Though, if I'm able to think of this, it's probably obvious to Yhwach and Uryu. Which means he's already got a counter set up. The big risk is that Uryu will be using Yhwach's ability in order to distribute his own soul. Possibly allowing Yhwach access to those soul portions in addition to his own. Meaning Uryu could inadvertently increase Yhwach's prospects by distributing tainted pieces of his own soul. Who knows.