When the video ended, the entire theatre has very different but very set of emotions that even the Chaos God's relish, the Primarchs, the demigod's and Son's look at what is happening with Horror, Despair but at the same time had the very feeling of awe and magnificence that can be stated to be outright heresy as the humans are being slaughtered like nothing, the very weapons that they thought marvelous turned to cinders as the being tore everything in its path, the very abilities of the creature defied everything and the horror of the potential it will bring if left unchecked.
One of the Primarch's snapped out of his stupor and turned to his father, "What did we just saw?", The Emperor, in all of his knowledge is flabbergasted at what he just saw, in all of its existence, has only seen this today but it left quite both disturbed and amazed at the creature tearing apart what seemed to be a pre-federation nation of japan, he immediately turned to his side to the Custodes and the personnel that watched this, all of them still reeling from watching the video.
He turned back to his friend and Right hand, "Malcador, Do it", his friend nodded and snapped his fingers, and all of them were put to sleep but also have their own memories erased. His Custodes collected them and brought them out to the infirmary and have their own memories change to more "acceptable" problems,
"My son's, it's better to look at this at another day, we have a galaxy to conquer", all of them wanting to voice their own opposition but he was right and they all needed to do something first before this happens again, gathering all their weapons and belongings, they all left the theater but Magnus look at the last piece of the video, with the fire's burning and the Monster or God, stood triumphant as he roars to the heavens with his armies of dragons.
"Maybe in the future, this will be answered", he turned and left as the screen shut's down, the lights turn off and the door slammed shut.
At some time later:
"Revelation, come look at this", the Emperor turned and he saw his friends holding what seemed to be a piece of archaic technology, one that was outdated as the use of crystals or even more favorable devices, but is still used in some form or the other as they seemed to be very aesthetic and cheap to use, but altogether removed by the purgation of the Machine's, "A USB? I thought this was lost forever",
But then he looks again at what he saw back at the room, the beast that seemed to even defy everything he believed about the earth, he only thought of this kind to be a work of fiction, a children's cartoon-like the purple dinosaur, but in this world that even demons exist and nightmares that no normal human could comprehend or even monsters of alien and human origins, everything is possible.
But again to the fact that this must be a potential universe where he doesn't exist or even none of the Chaos God's do is. And that brings him to more questions rather than answers but not at this time.
"This will come at a later time, keep it safe and sound and none must hear of this", Malcador nodded and it disappeared without a trace. "You have my word, old friend".