Young Writers Society

So I need some help. I am writing a fantasy (a traditional-esque fantasy, you know, medieval style) that involves a strange (maybe) and dark power. I have no clue what it is though, but here's what I got:

1. It's inherited (sort of like a curse)
2a. It does not manifest itself until the protagonist is a certain age...
2b. at which point it comes suddenly, and the poor dude is EXTREMELY vulnerable for one hour while the power takes full effect/grabs hold
3. Its involuntary
4. It's dangerous, extremely so, to both the "wielder" and those around him.

I'm thinking that once the power arrives, the protagonist’s eye color will change. (From both brown to one gold, one brown) but it sounds a little cheesy to me. What do you think?

So that's all I've got. I don't have any ideas about what the power actually IS, which is why I need help. What power/powers do you think are best associated with the information above?
I was thinking visions/telepathy/brain power but those don’t really fit with the story, and any case they don't seem all that powerful to me.

My first reaction was that it sounded like werewolves, but werewolves need to rest a few decades.

My advice would be to comb through fairytales and see what people considered scary enough to threaten their children with. And don't forget the cultural impact.

What about something spiritual, like the ability to act as a conduit for the dead? Depending on who/what possess the character during that time, the potential for murder is a very real possibility, and if you make malicious spirits the ones most likely to possess a person, the the danger becomes more inevitable than theoretical.

Hey people, thanks for all the feedback!
I think I’ll go with the ability to manipulate darkness, (metaphysical/spiritual/mental darkness) which carries over in his ability to enter other people’s dreams. (Although how dreamwalking is dangerous, I don’t yet know…)
Also something else, called a “Dusk” state, in which he essentially looses the control to regulate his attacks against an enemy, as his mind/soul “leaves” his body while this happens, or he gets lost in the darkness which he is supposed to control. Although in this state his body is nearly invincible, a plus, there will be quite a few injuries once he “returns” to it. heh.
Does this make sense? Is it goofy? Sould I change/add something? What do you think?

I think that sounds realy cool. Dusk state sounds like a really interesting spin on something slightly mythological, which I love.

Dreamwalking is traditionally dangerous in a couple of ways. For one thing, it leaves the body almost completly unprotected, and it could be hurt or even waste away if the dreamwalker doesn't return. Related to this, it is remarkably easy to get drawn permanently in the dreamword, which would be bad.

Also, messing around with someones dreams could possibly be harmful to their innermost phsyche, or even their souls if you want to use that term. You could do all kinds of things from within peoples dreams, but the lasting effects could be bad news.

Hope that helps!