no man’s even seen the face of his foe, no he ain't made of flesh and bone he's the one who sits up close beside you, girl, and when he's there you are alone
So how do they do it?1
(Part 1 here.)
That’s a premature question. To ever really understand a how, you should first know the why.
Demons don’t want to kill you. They don’t mind, of course, they haven’t any compunction, but that’s not really the point. The tanner has no job without the fact of animals being killed, but the killing isn’t the point, just a necessary adjunct.
Demons just want human souls to suffer and wither. Or wither and thereby suffer. If you actually die—or not—is of little consequence. When you’re an effectively perpetual being, if a human actually lives for another eight days or eighty years is of little import; the deep scale of time makes the two effectively identical. Does a redwood care if a beetle dies young? There will be another there the next time it looks.2
The point is the suffering. Killing the body ends the suffering. Moreover, the longer the suffering—generally!3—the more resentful and debased and cheapened the person becomes, leading to a stronger likelihood of the person, on death, shuffling off to an afterlife of continued suffering. Hurt people hurt people, they say for a reason; Job made the books because he’s an exception, not because he’s the rule.
So there’s the why. Demons are about fear and hurt and self-loathing (especially self-loathing!) and degradation and that change in the look in a person’s eye as time goes on. Twinkle, confusion, desperation, dead.
Let’s leave aside what a demon is, for the moment, in favor of what one does. Basically, it talks to people. That’s the whole deal. Maybe once in a few centuries some favored paragon will zot to another plane and try to put enchanted steel to one. But demons talk to people every damn day. They talk. That’s their power.4 They’re convincing. And very, very clever.
They lie, of course. But no more than anyone else does. Telling the truth is much more effective, and there are an eternity of ugly truths to direct peoples’ attention to. Eventually the truths always shade into something else, sure, but the foundations are always truths. “You want this” so easily becomes “you deserve this” becomes “that’s yours” becomes “take it.”
A demon talks to you, at first telling you the things you want to hear, then the things you don’t want to hear, and finally the things you can’t unhear. Depending on the demon, or the demon’s favored approach (each has a favorite approach, depending on what end the demon finds most satisfying and what, in the past, has worked best for it), that talking can come in many forms. The grief-stricken mother might find her dead child’s voice coming out of the mouth of another woman’s child: “Mama? Why couldn’t you feed me?” It could be the popular preacher you just really connected with, and if you just send out your prayers the universe will pour wealth upon you. Maybe it’s that intrusive thought, about how you’re not good enough for her and she’s always looking at other guys and if you leave her alone for a minute she’ll run off so better not.
That’s what they do. It can be sweet and soothing, or reproachful and rebuking. What it always is is either:
telling you it’s okay to do something you already want to do, or
blaming you for something that has already happened.
People don’t generally need much more encouragement than that. How hard is it to tell someone who feels bad that it really is his fault that that bad thing happened? To tell the mighty how all those rubes deserve what they get for being so weak? To tell the cockscomb to linger another moment in front of the mirror? To tell the melancholiac that it actually is of no use, and best to stay shut in and lie down for another day in the dim and stinking room? To tell the well-heeled to skip the almsgiving this week, because those wretches would probably just use it on dice and arak and never bread and besides almsgiving isn’t really a mandate for actual money, it’s symbolic of the goodwill in your heart that of course you have, right? For the deserving ones, at least?
Demons talk. That’s their weapon, at least here on this plane and this world and where everyone you’ve ever met will ever meet them and never know they’ve met them.
“Black Soul Choir,” 16 Horsepower, supra. No, really, how does Mr. Edwards do it?
Yes, a redwood can look, smartass.
We all want to think our sufferings make us stronger. Sometimes suffering is just suffering.
It should be their Monster Manual entry, too. “Demon: whispers shit into your ear until you hurt yourself or someone else. Then makes you feel bad about it so you do it again.”