What does the narrator mean by the "God who emerged from a volcano"?

Question

During route B, in one of the additional cutscenes, the narrator (I'm not sure if this is 9S, so I will stick with "narrator") mentions a

god, who came from volcano, and taught machines about emotions.

What is this about? Most of those cutscenes are telling us a story of machines gaining self-awareness, but this particular part is not exactly clear.

Currently, I have only one theory:

Appearance of god from volcano is symbolic description of server destruction in Mt. Ka'ala during Pearl Harbor Descent. After this, there was no central hub to control all machines, so they've started to become sentient.

If there more solid theories or facts, I would like to hear them.

Answer 1

Apparently, it is a direct reference to a novella titled "The Fire of Prometheus", written by the director of the Nier games, Yoko Taro. The entire story can be found here.

The novella is a relatively short read, but to summarize:

It tells the story of a machine that awakens within a mountain and attains sentience. Upon seeing other automatons that lack sentience and attempt to fight it, it instead awakens them to sentience, as well, then merges with them, eventually becoming an enormous conglomeration of machinery. Eventually, they, as it begins referring to itself as a plural entity, blasts a hole in the ceiling of the mountain, which gives off the appearance of being a volcanic eruption. Upon witnessing androids and machine lifeforms fighting and realizing they, too, lack sentience, the merged entity decides to awaken these automatons as well, teaching them the desire to live and the fear of death.

Yoko Taro himself made the connection during a 50 question interview he did for NieR: Automata. The entire transcript is provided in this reddit thread.

The relevant part is here:

Q46. Who is the ‘god that emerged from the volcano’ as depicted in the picture books?

See “Prometheus’s Fire”, a novella featured in the book that comes along with Drag-on Dragoon 3 limited edition.