Explanation on House Einzbern

http://pastebin.com/JU2Apbri
https://www.reddit.com/r/fatestaynight/comments/3yirhx/all_vn_spoilers_what_happens_to_the_einzberns/

The Einzberns, were created in 1 AD/CE, by the apprentices of the user of the third magic, with the goal of replicating their master, and saving man kind.

9 Centuries of failure later, they made Justeaze, who was an accident. When they made her they didn't expect anything but they got something with the talent of their master or even above it.

However the apprentices weren't happy about it since even though she could use the Heavens Feel she was an accident, but if nothing else they got their third magic, and decided to mass produce homunculi thinking they could produce something better than Justeaze if they could produce her. Anyway they were tired and they made Acht who would be the "father" of all the homunculus. Incidentally Acht is the body/terminal seen in FSN and Jubstacheit is the control system/golem thing that is also the castle or something.

Anyway Justeazes problem was that she took several years to "save" one person so they couldnt save everybody (which was their goal, not reaching the root). Also while Justeaze was ageless she was pretty weak and couldn't leave the castle. Her intelligence and mind also didn't age at all so for her it was like "seeing the same day for eternity."

And if she went outside to experience things, she would be basically committing suicide.
So they made something that exceeded humanity but couldn't save humanity, and they reached the limit of their ability.
So some apprentices left, and some committed suicide.

The homunculi who were left behind followed the mission. Save humanity, make a miracle reappear. All homunculi made after used Justeaze as a basis. Its why Acht is the only male seen.

So 500 years after the magi were all gone, the homunculi make a plan to use Justeaze to reproduce the Third on a wide scale. They figure they can't replicate her after all, so they were gonna keep her forever, but they're robots and will pick whatever has the highest probability of success so they reach a consensus to use her, Jubstacheit was the only one against it.


Since Justeaze can only use the third on one person over years or decades, they use her to make a large scale ritual to save multiple people at once. They plan to disassemble Justeaze's circuits, and make a "humanoid universe" which is the great grail.

But they realized they needed they help of a human  because they can't enter human society on their own, and in 1800 they find Zolgen.

Despite having mostly given up on trying to eliminate evil and save humanity by that point, he took the Einzberns as his last hope.

So they have Makiri as a partner and found Tohsaka as a cooperator and built the great grail, but they needed magical energy and a lesser grail to control it. So theMakiri and Tohsaka make the grail war to gather magical energy, Einzbern makes the lesser grail.

And after 10 years they do the grail war and it works, but they fail because magi fight over who gets to use the grail, because Einzberns are pure robots who didn't realize humans are going to do that.

So the Einzberns have no Justeaze so while working to restart the great grail they go back to their original focus on manufacturing a perfect homunculus, bringing about Illya and Iri and all that. Also Nasu mentions Jubstacheit shutting down after Illya dies which was mentioned in episode 15.

Nasu gets poetic and makes a comparison;
there was a doll that said "I love you", you'd realize pretty soon that it's just repeating prerecorded phrases and the emotions it expresses are fake, and you get tired and throw it out, right? Well that's because you're looking at it from a human perspective, but machines don't lie and just innocently do what they've been told to do.
And a machine loses its value (life) not when they become obsolete, but when humans can no longer stand that purity. (Gil comments on human incapability to understand the purity of homunculi in episode 14)