system
Given the following post, respond as if you're commenting on Reddit:
human
[Prometheus] Why did the Engineers want to kill humans? Why did the last one attack? Why did they make the black ooze? What was it? Where did the animals come from?

(Out of character disclaimer: I essentially didn't understand the entire last half of this movie.)



What were the urns? What was that giant head? Why did the murals start changing? Where did the Engineers go? How does all of this relate to the Xenomorphs? Did the Engineers create them or discover then? Were they trying to exterminate them or make more? What was the black goo disease that made Holloway sick? What was the squid creature that was cut out Dr. Shaw and attacked the Engineer? I have so many questions on the information retrieved from this expedition. Do we have any answers at all?
gpt
The best source seems to be from behind the scenes explanation, but the general gist that Scott and the screenwriters were trying to imply was that the Engineers seeded Earth with human life, checked in on us at some point in our history and saw that we were misbehaving quite a bit, and decided we should be wiped out before we spread out of control and ruined the planet and the rest of the universe.

The planet that the crew ended up on was the Engineer's equivalent of a weapons lab/military outpost. The black goo was a biological weapon they developed for the purpose of cleansing planets by seeding them with Xenomorphic creatures. They were about to launch a ship filled with the goo to bomb Earth, but the creatures got loose, and everything went into lockdown/hibernation mode until the Prometheus crew arrived.

Scott has said that the more specific details he had in mind, was that the Engineers tried to set us back on the right path first by sending an emissary to Earth about 2000 years ago to help guide us. That emissary would be Jesus Christ. Unfortunately we end up crucifying him, and the Engineers back home are like "Holy shit" and decided we were beyond saving at that point and decided to go with the extermination plan. This is why a timeframe of 2000 years is specified in the movies.

He did stress that this isn't set in stone as the final canon though, cause basically him and the screenwriters merged different ideas together, and left thing open ended as the true story so they could elaborate on the details in a later chapter (probably in Covenant) or just let the audience come up with their own interpretation if they never got around to it.