My brothers, do not make the mistake of thinking yourselves prepared. I have stared into the face of our ruin, and it is not a face. It is a mouth. A mouth containing a billion teeth, and each tooth is a living thing, and each living thing is a horror built only to kill, and when the mouth closes it shall not be to honour the supreme Emperor, or sue for peace, or discuss terms. It shall be to swallow our Imperium whole.
We call them Tyranids as if they're a race, another xenos clan to be faced down and cleansed. In the face of horror we cling to our sciences, our labels, little realising they do nothing but drown us. We'd do better to call them a disease. There is no better analogy. I've seen the hive ships, brothers. Barbed horrors scuttling forth to kill, bloated vermin writhing back to be absorbed, their bellies full. I've seen the forests picked clean of life. I've seen the biofleets draining the water of teeming worlds, the vortex mouths guzzling the prairies. I've seen shadows moving in the Warp, the tentacles stretching out of the darkness beyond the Eastern Rim.
This is the End of Times, brothers. Death approaches, and it is not at the hands of a ravening horde nor any army of contemptible aliens. Our enemy is a single intellect. A single gestalt consciousness, more ancient than we can conceive, more massive than we can measure, a single mind that has not one body, but a trillion. An all-seeing eye that has no shape and no form. How can we fight such a thing?
I will tell you: until the last breath. If we can but delay that great maw from closing around us, then we have achieved what countless empires, countless worlds, countless galaxies, have not. I say this not to terrify you. I say it simply so you understand, simply so you do not waste your time with luxuries such as hope. There is no hope. The Great Devourer is upon us. Let us see how long we may restrain her jaw.
We cannot live through this. Mankind cannot live through this. In a single day they have covered this planet with a flood of living blades and needle-fanged mouths. Kill one, and ten take its place. If they are truly without number, then our race is doomed to a violent death before every shred of our civilisation is scoured away by a force more voracious than the fires of hell themselves. Death! By the Machine God, Death is here!
— Last writings of Magos Varnak, Warhammer 40,000
They learn that engineered metal — though itself inedible — often indicates that edible beings live inside. They learn that inedible metal spacecraft point the way to and from worlds full of edible beings.
Adapt they can, but only if it lets them eat — and eat now. They store nothing. They plant nothing. They eat their dead and wounded. They are an engine of entropy.
They have no higher conscious purpose. They have not the least concept of planning or investing. You would think that something that voracious would learn husbandry, conservation. They have not.
The Hive kills host after host. If ever it asked a question, it would be: what is left to eat? It uses, it throws away. And would you even want to teach gorgons husbandry, so that they might plant people gardens for future harvest?
Do remember: entropy is a force of nature, too. What is natural need not be benign. The Hive is nothing less than the living, eating incarnation of the Ninth Level of Hell.
— Don Jose Maria Cordillera, Tour of the Merrimack: The Myriad
I used to think that defeating the Zerg would take precise military maneuvers, clever tactics and strong leadership. I was wrong. You can't out-think the swarm, you can't out-maneuver the swarm, and you certainly can't break the morale of the swarm. I hate to admit this, but I could do my job just as well if I ordered all my men to simply shoot anything that moves.
"They're like moths drawn to the flame of battle. They live only to consume and destroy, like... hungry moths."
— Palutena on the Aurum, Kid Icarus: Uprising
"You still don't understand what you're dealing with, do you? The perfect organism. Its structural perfection is matched only by its hostility. ... I admire its purity. A survivor... unclouded by conscience, remorse, or delusions of morality."
Can there be peace between us?
NO PEACE. WE MUST FEED. ONLY WHEN WE HAVE FINISHED CONSUMING THIS GALAXY WILL WE DEPART TO CONTINUE OUR LONG JOURNEY.
—Stellaris, on contacting the Prethoryn Swarm
After quashing all resistance in an area, the Reds set about their true work: systematically stripping an area of all biological resources. These include any human (or Grey) survivors, as well as the dead (even piles of ashes). Using a variety of strange, advanced, and frightening tools, the Reds collect all animals and plants even microorganisms in the area, before going so far as to strip the soil of nutrients, ensuring nothing will grow there again. Once an area is thoroughly harvested, the Reds move on to the next target.
—"War Between Worlds - Post-Apocalypse," The End of the World: Alien Invasion