Very Interesting read. Though I do feel that the sacrificial liquid and the black goo are different. When the sacrificial substance contacted air, it began to disintegrate. The black liquid did not do this. Another important fact is that in the ampule chamber we see a green crystal (or the sacrificial bowl if you are looking at the art book) on an alter, almost being given up to the Deacon/Xenomorph. This might symbolize that the Engineers are giving up their gift from God for another gift from something more... sinister. I do strongly believe that the Deacon/Xenomorph is the destroyer, the Devil of this universe. However it leaves one wondering not what the origins of the Engineers or mankind are, but that of the Deacon.
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