"Ignore the macho bravado you've overheard drunken marines spout at bars - especially those with no scars on their faces and all their limbs intact. They are cocky and alive because they haven't actually seen a xeno in real life. If they knew anything worthwhile about these things, they would be shaken and reserved. If you see a xeno, you do one thing: run. You don't stand a chance, you never did and you never will. You think you've got superior firepower in your hands? Use all your big and fancy toys to cover your escape, but get the hell out of there."

―Description of a Xenomorph (from Alien: The Roleplaying Game)