I think this is the closest I get to a topic about the ritual and it does have connections to the individual question as well I'd say. I don't know how far this was discussed before, but replaying the game in Japanese actually made me notice something I didn't notice that much before in the text about the descent of the holy mother.
The translation for the Descent of the Holy Mother text is rather free and sadly looses one important aspect...at least I didn't notice it before, that is that the original text makes the sacrifices much clearer and a little more poignant I think:
The First Revelation
And the Lord said, in the time of strife and fullness, in stillness, purify through my wrath.
With the White Oil, the Black Cup and the blood from the Ten Hearts of Sin prepare the ritual of Liberation.
The Second Revelation
And the Lord said, together with the White Oil and the blood from Ten Hearts, offer up your own blood as well.
By doing so you will attain Liberation from the shackles of flesh and attain the powers of the second world.
Through Nothingness and Darkness birth Gloom,
and prepare through Despair the Giver of Enlightenment.
The Third Revelation
And the Lord said, by the Temptation through sin you will return to the great Origin, and under Observation of the unenlightened demon you must circle towards the time of Chaos and line up the Four Atonements.
If this be done, the Road to Recurrence shall open.
The Final Revelation
And the Lord said, and the One who will become the Body of the Mother, and the One inheriting the final Enlightenment, they shall be released from the flesh.
If this be done, through the 21 Sacraments, the Holy Mother shall appear from the Land of Plenty and bring Salvation to the Land of Sin.
This is a rather quick translation, so bear with me if it isn't Shakespeare.
The blood from the Ten Hearts of Sin was gained from his first ten victims, but it was never mentioned that the Practicioner/Conjurer had to offer up his own blood in the ceremony as well to complete the "ritual of Liberation" (which is called Assumption in the translation). This is when he gained the "power of the second world", which can be the afterlife, but also the world of dreams experiences through Silent Hill.
He then killed Peter Walls (Nothingness), who had probably seen nothing when he claimed to have encountered God, and Sharon Blake (Darkness), whose life was darkened by the meddling of the Cult. They probably let him know about the place of Toby Archbold (Gloom), who was depressed about the current hard times of the Valtiel sect, and thus they "birthed" his demise.
He continued with preparing Joseph Schreiber (Despair), by leading him on the path to Enlightenment about all the events, but led him to desperation when he trapped him in his room and made him nothing but a "Giver of Enlightenment" to the next tenant.
Like in the 3rd Revelation, he circles down the spiral staircase of the 4 dreamworlds. First he is approached by Cynthia (Temptation), who 'seduces' men to sin, killing her leads him to Jasper Gein (Origin) and back to his own Origin and the origin of the cult which started it all. He performs his next act under the eyes of the former guard of the Water prison, Andrew de Salvo (Observation), who knew nothing about the greater scheme but was still a horrible person. And finally he reaches the probably slightly insane Richard Braintree (Chaos) who himself has violent tendencies. In this order he lines up the 4 Atonements. Then the Road to Recurrence opens and we have to travel through all the worlds again to reach the core.
Finally, being the only one who was ever really nice to Walter, Eilenn (The Mother's Body), shall become the container for the descended Holy Mother driving her insane, and, being the one who was enlightened about the events by the Giver and by traversing the worlds, Henry becomes the One who receives the final Enlightenment. This seems like, in spirit, they would become the formula from which the Holy Mother is formed.
Then the Holy Mother appears in this world in the flesh from another world and cleanses it in her image.
Maybe this was actually clear to everybody playing the English version from the get-go, but somehow I didn't put two and two together until I read it in the original Japanese.
So, what I'm getting at is that Eileen and Henry are more horribly disfigured because they must be completely stripped from their flesh according to the ceremony.
Now on a tangent, isn't the whole ritual kinda flawed from the beginning when it talks about the Ten Hearts of Sin and Walter sacrifices two innocent children?