Nightmare Fuel / Megaton Rainfall

• The plot of the game can be described as a Cosmic Horror Story in which the human race plays the most important role in the universe, without their knowledge. The Signer, for reasons unknowable, has declared humans to be the only intelligent life in the universe worthy of existence and plans to erase the rest. However, since he can't make meticulous changes to the universe, he uses you as a Human Weapon to exterminate the unworthy lifeforms, the intruders fighting for their right to exist in competition with humanity.
  • In the ending, after you successfully genocide the intruders, the Signer decides that humans will likely never be able to fill the universe due to the sheer distance of other stars from theirs. The only way, he decides, that they will be able to fulfill their purpose, is if he erases the entire universe and fills it with infinite clones of Earth. Now all of the human race's progress is rendered pointless in an instant. There will be nothing new in the universe to find, no alien species to meet, no meaning to be discovered. Only an endless amount of themselves. Just imagine the existential depression that would eventually befall most or all humans alive. This may be one of the worst fates the human race has ever been dealt in fiction, nevermind that all other intelligent life in the universe had to die for this to happen.
  • The Signs scattered throughout the universe reveal the truth about existence as a whole. In as concise an explanation as possible, existence is an endless tree of intelligent beings creating universes in their minds full of intelligent beings that create universes in their minds. This pattern spawns from a test developed to find out if a creator, a God, exists: create a universe "below your feet", let it evolve, and see if conscious beings are born in that universe with intelligence equaling or surpassing your own. When you succeed, you will know for certain there is someone above you as well, even though you can't see them. Depending on your perspective, this revelation can be absolutely nauseating, some sort of relief, or both.
    • Fridge Horror: The "easy way" to find out if a creator exists is if the higher being who made your universe decides to sign it, as this universe's higher being has; then you just have to find the signs. "Because what god would be so cruel as to create conscious beings and then let them live and die without telling them why they exist?" The Signer himself would. The Signs in this universe are scattered across planets far, far away from Earth where the Signer knows that humanity would never be able to reach them. As the cherry on top, after you find each Sign, you're forced to destroy it. The truth that the human race has been searching for since its upbringing was there all along, just out of reach for them, and taken away by the only one who can reach it at the behest of the one who placed it.
    • More Fridge Horror: The intruders are aware of the Signer's existence, and thereby of the "tree" of existence. That means they either found the Signs with their space-traveling technology, which is unlikely considering the planets housing the Signs are all untouched, or their race's philosophers or scientists successfully created universes "below their feet" filled with intelligent life. You, by the end of the game, seem to have eradicated their entire species. What do you think happens to a universe when the one who created it in their mind dies?
    • Another case of Fridge Horror: The Signs imply that the Signer needs humanity to act as a sort of a computer to find the Signs in his universe. Which means he might be wrong and he in fact created an entire universe to try and find something which doesn't exist.
• You are an immensely powerful Flying Brick with below-ideal control over your power and are FAR more of a danger to the human populace than the intruders could ever hope to be. Miss one little shot? BUILDING GONE, DOZENS OF PEOPLE DEAD. God forbid, miss a Gigaton Blast while aiming downward? Kiss that city goodbye. The civilians' cries of terror will haunt you for your entire playthrough.
• Exploring space evokes a unique, haunting feeling of loneliness. Every planet you find is no more than a barren wasteland or a gas giant, and the only breaks in monotony are the Signs and a black hole. The fact that such an incomprehensibly large space with so much in it is still so empty, cold and barren is mystifying.
• The protagonist themselves isn't dealt a good lot at all. The Signer's dialogue to them in the prologue implies that they were formerly a human, and were dragged away from their former livelihood into a Cosmic Horror Story where they're cast as a Human Weapon and forced to discover the secrets of the universe that they may well be better off not discovering. Sure, you have some fancy superpowers, but so what if your existence is nothing but murdering aliens, accidentally killing your once-fellow humans and drifting through the universe all alone?