On my alternative Prometheus movie plot, the humans spaceship arrives to a huge Engineers environment on a far, really ancient planet. All the alien fortress is a living biomechanoid system, and seems to have been waiting for them. The ovoid domes keep inside all different spaces, from the spaceship ports to the Engineers breeding labs, and some gigantic hall where the ancient Space Jockeys just sleep, waiting for their creations in order to meet and checking them.
The human scientists will discover a terrible truth. All that place is just an automated system, programmed by older creatures who created the own space Jockeys ages ago, when universe was younger. There is no god to meet at, to ask for, to solve any question. Just ancient alien drones programmed to analyze their creatures, and their analysis is really devastating for the expeditionaries. Humankind is another failed attempt and must be purged. The ancient gods who created us, there, in the darkest and coldest reach of space, just have rejected their sons and send them a message of death through the stars
I quote, "The Destroyer, commonly known as Xenomorph, is a biological weapon conceived just to purge and clean all failed test species on their homeworlds. High adaptable and intelligent, it´s however a really limited creature, with a short, fast life cycle, absolutely specialized on terminate all creatures during the few hours its agressive metabolysm rages to their end, when the creature finally encloses itself into a sort of cocoon and just crystalizes, keeping the traces of host DNA to be recovered by Engineers. During a whole planetary extermination, when the destroyers reach a certain ammount, some of them just mutates into a bigger creature, commonly known as the Queen in order to increase the number of eggspores and balance their fast life cycle."