The Mind Worms are the natural defenses of the living Planet—the white blood cells, if you will. In a world in which unassimilated thought represents danger, the Mind Worm seeks out concentrations of sentient mental energy and destroys them, ruthlessly and efficiently.
— Commissioner Pravin Lal - "Mind Worm, Mind Worm" , Sid Meier's Alpha Centauri
You are not in Kansas any more... you are on Pandora, ladies and gentlemen. Respect that fact every second of every day. If there is a Hell, you may want to go there for some R&R after a tour on Pandora. Out there, beyond that fence, every living thing that crawls, flies, or squats in the mud wants to kill you and eat your eyeballs for jujubes. We have an indigenous population of humanoids here called the Na'vi. They're fond of arrows dipped in a neurotoxin that will stop your heart in one minute. As head of security, it's my job to keep you alive. I will not succeed... not with all of you. If you wish to survive, you need to cultivate a strong mental attitude. You've got to follow the rules - Pandora rules.
— Colonel Miles Quaritch on Pandora, Avatar
The krogan evolved in a hostile and vicious environment. Until the invention of gunpowder weapons, "eaten by predators" was still the number one cause of krogan fatalities. Afterwards, it was "death by gunshot".
TRAVEL ADVISORY: The ecology of Tuchanka is deadly. Nearly every native species engages in some predatory behavior; even the remaining vegetation is carnivorous. Travel beyond guarded areas is strongly discouraged.
—Description of Tuchanka, Mass Effect 2
Ramden: Down there they have anti-tornado warnings.
Ramden: Areas where there isn't currently a tornado.
They got Hood-damned demon farmers! Sowing seeds, yanking teats, spinnin' wool - and chopping strangers to pieces! Gesler, old friend, I hate this place, you hear me? Hate it!
— Stormy, Malazan Book Of The Fallen
Char. If hell ever existed, this is it. Oceans of fire, tectonic storms, and an atmosphere that will burn a man alive.
— General Warfield, Starcraft 2
This is a Class 1 quarantined planet. The threats we will be facing are real. Everything in this planet is evolved to kill humans. Every single decision we make will be life or death.
— Cypher Raige, After Earth