I'm currently writing a story about a human on an alien world, and every single species is completely terrified of him (despite him being a ten year old)! How should I go about their perception of him?
Well, look at it like this; imagine how would you feel in the presence of a sapient velociraptor that only speaks in Ancient Greek. The point I'm trying to make is that most fear is that of the unknown. The aliens would be more afraid of what they perceive that kid might be than of what he has actually shown himself to be. With a language barrier in place, that becomes even more the case.
Imagine you are suddenly confronted by an alien, all the worries of wondering if the alien is going to probe/eat/kill you, pass on diseases, bring the rest of his Alien race to turn humans into slaves or even mate with you. There you go!
That, and if they research what the humans have done to each other over the course of human history they'll have plenty of reasons to be terrified of this one human. They don't know whether or not he's a psychopathic maniac. Though I hesitate to accept that every single species, or every single member of every single species would be terrified of him. Not everyone in any given species will share the same beliefs. Maybe some of them are willing to give the boy the benefit of the doubt and trust him rather than treat him like he were the harbinger of the incoming apocalypse.
Every good lie has some truth to it. Have the aliens heard anything about humans before? Maybe any information they have is what terrifies them.
You could have a lot of fun writing it as they have learned fears from watching our satellite cable. They could think some humans have superpowers like heat-vision or the ability to fly. They think we enjoy arguing and flipping tables as seen on many reality tv shoes. The news stories of germs and fear of them spreading. Honestly you could have a lot of fun with fear in misconceptions of another culture. What if the aliens are vegetarians. "The Human opened it's mouth! Run!" the alien screamed, pushing children out of the way to escape. "Humans eat flesh, after they've lit it on fire! I don't want to be one of their happy meals, out of my way." cried a large slime alien, sliding away from me as fast as she could.
Maybe all the species on the alien world are really tiny, so the ten-year-old human boy looks like a giant to them. Every step he takes kills hundreds of them - of course they'd be terrified!
Since you said every single species on this alien world is terrified of him would seem to imply the human looks different than any other creature on this world. If you have not already decided on the various creatures of your alien world then maybe the human can share features of the fiercest creatures they are familiar with, all the things that make their own known frightening creatures frightful. Of course another option might be to dress up your alien in a Halloween costume and since he has no other clothes, assumption on my part, that is all it takes. To explain this a little, I often wonder what my pets think of my different clothes I wear, shorts to slacks, to jackets or T-shirts; pets learn to accept that, but we must appear to be a chameleon to them.
Or to take a sci-fi slant on @minstrel 's great idea, perhaps these various alien species are all sentient microbes who are being systematically murdered by the boy's immune system. Maybe the boy is completely unaware life even exists on this strange planet until the intelligent microorganisms find some way to communicate with him (or perhaps start waging war via disease). It could seem like the contact came straight out of thin air! (...particularly if the planet's atmosphere is less dense than Earth's ... and back to the pungeon I go.)
I think it'd be fun to write about how every time the boy sweats, farts or cries the aliens think he's releasing biological weapons.
Must resist urge...to make fart jokes...related to Skyrim! My immature side wants to make a bunch of fart jokes, but I'm not sure which would be best to use.
From who's point of view is the story told? If it is from the boy's, he would have no idea why the aliens are frightened so neither would the reader. I suppose you would have to resolve this issue eventually. You could have a totally non physical reason. Perhaps the aliens have a deep-rooted cultural belief that no life exists outside their own world. The presence of the boy would undermine everything they knew and took comfort from, and make them face their own doubts and fears.
Hehehe this sounds like a funny story I just imagined someone seeing your MC and going "ARGH!" and fleeing hehehe
What if they are scared because they met a human before. Finding out who it is could be a major plot point.
He might simply be significantly larger than the planet's inhabitants. His strength might be exaggerated because of a gravity difference. Viewing the creatures around him the way a ten-year old might view insects on Earth, he might set about harming them for his amusement. This is more straightforward than some other suggestions above, but seems likely. Can he breath on this planet? How intelligent are the entities he encounters? Being on another planet by himself, I would think the ten-year old would be exceptionally scared as well.
Humans have teeth, nails, opposable thumbs--all things that can cause harm to others but that the aliens might not possess. Humans might also be stonger, faster, or bigger than the aliens or possess better eyesight, hearing, etc. All the things that make other creatures scary to us, the advantages they have over us, could be advantages humans have over this particular species of alien. And how we perceive these creatures is how the aliens would perceive the boy.
Both of these points are really good - they're gonna judge him on humanity's history, if anything, but I also doubt the entire species would have that fear. Even two monsters in Monsters, Inc. accepted Boo, remember.
