Dreizehnn
I am confuse, my understanding of the Angra Mainyu in the Grail was that he wasn't the original. He was supposed to be a child which a tribe blame all the world evils and torture to death. That was the reason the Einzbern where able to summon him, because he was a fake divine created out of misunderstanding + that was also the reason he was so weak. Finally he got all his power after living inside the Grail. Maybe I am confuse but based on my knowledge he's not truly a divine spirit.