That has to be a clue, but it's nothing anyone else couldn't do if they could fly.

If you try to look at a specific part of the forest that you have seen before, do you still get the headache?

Nope. There's forest. Denser in spirits that the forest around it - I think - okay, headache if I try to notice that...

Okay, we should be able to do this by elimination.

She points in a direction, chosen arbitrarily. Do you get the headache if you try to look there?

Nope.

Great, it's not that way.

How about there? A slightly different angle. Trivially repeatable, though it might get boring after a few iterations.

They find it before they even get too bored.

This seems too easy. Are they that confident the Enemy will never have anything that can fly, or are they just expecting he won't know there's anything to look for?

Might be mostly meant to protect against orcs? I'm not sure why the Enemy doesn't do more coming out and smashing things in general, I don't know why people aren't prepared against that.

My money's still on there being some cost we don't know about. We're probably not lucky enough for it to be a weakness we'd notice if he did much smashing.

Maybe the queen here will know something.

If she's a Maia, bet she will. They know a lot, they just tend to be bad at explaining, and if she spends lots of time around Elves she'll have to be better than average.

Well, here goes finding out.

They land just outside the boundary and try not to look threatening while walking headacheward.

And someone pops out of the trees and lands on the ground. They are not armed. The dozen people that have arrived in the trees around them, though, and that would be invisible if Amber and Irisse could not see the connection-lines, are probably armed. 

Probably. Well, the visible person has got to be the one to talk to.

You want to do the talking, or should I? We don't know how much they'd care about formality, and only one of us is from the relevant royal family.

Yeah, yeah, good idea. 

Hello, she says, I am Irisse Nolofiniel, granddaughter of Finwe; my people are newly arrived here, and heard word of yours. 

Hello, says the stranger. The Valar did not tell us to anticipate your arrival.

The Valar are grieving the destruction of Valinor and were very distracted. They told us we had their leave to depart. 

That's definitely a way to put it, yes.

Are you in communication with the Valar?

They speak sometimes to the Queen. You are not of the Eldar.

No. My name is Amber, called the first of Men in Arda.

Cautious nods.

Why are you here?

We have come to stop the Enemy, Irisse says. We would like to be an ally to your people in that.

The King and Queen are King and Queen of all Beleriand. Will you acknowledge them as such?

She pauses. I imagine that meeting them and hearing more of their achievements and their rule will inspire the respect we would require to make such a commitment.

If they're rulers of the whole thing, what's Melkor, an inconvenient rebellion? That would maybe be a bad idea to think out loud.

How many do you number?

A hundred thousand, Irisse says, and as many allied.

Where are you settling?

At the vale where the Sirion turns south.

There are people there already.

We are trying to get along with them.

We're here to oppose the Enemy, that gives common ground with a lot of people.

We were not told to anticipate your coming, says the guard, again, suspiciously.

When we left for this continent we had yet to hear of your presence. Until recently not even we anticipated our coming.

The King and Queen desire to know your aims here. 

We want to stop the Enemy, Irisse says. We are an ally to any foe of his. 

Will you swear to do no violence in Doriath for the duration of your visit here?

Would you accept a promise of no violence as long as no one does violence against us? I trust this would have exactly the same effect.