I agree it was dangerous. But even the worst-case result was less so than not doing it. Ungoliant can- I strongly suspect Ungoliant can destroy people so thoroughly there is nothing left to go to Mandos, and the dragon isn't actively malicious. I do wish I could have explained more in advance.

Or refrained from allying with those who will swear themselves into senseless wars. Leave me to think.

She floats carefully back across the border.

The fight is still ongoing and hard to follow.

Downright impossible without borrowing Elf vision. Every time a claw lands there's a spray of darkness or brilliance, depending, and instead of fading the results stay behind to mess with the view. They can at least make out the general position, which seems to be getting farther away from Doriath.

That's something.

Better than the reverse.

And there's no way this doesn't drive away every potential challenger less reckless than us. Melian'll have her demesne sooner rather than later.

Not that it necessarily matters, now. 

It means if the dragon comes back afterward she could probably hold it. But it's mostly a good thing. The Enemy might try to follow through on the implied threat.

He swore to, didn't he?

She shakes her head. What he said was he had a way to destroy Doriath and wouldn't use it while they had the Silmaril. If I were in his position I'd rather use that on us, but it makes sense for Melian to not want to gamble.

If he has a way to destroy us why wouldn't he have used it already?

That's been a question since before he knew about magic, when he definitely believed he could. And I can't picture what he'd expect to work against Doriath but not us...

Knows exactly where they are, if it's something slow to put in place....

And has known for a long time. Maybe it's a Vala magic thing instead of a practitioner magic thing?

That'd explain the delay. There are obvious ways to do it with practitioner magic, though -

Ways that wouldn't be just as easily used against us?

No, but ways easy enough that the fact he hasn't done it demands some kind of explanation -

So if he moves against Doriath we know that whatever his reason is, it's less important to him than following through on a threat.

Yes.

By the time he tries anything he'll be contending with them slowing him down, which he'd know to expect, and with Melian being a second type of "one step below a god," which he wouldn't. Hopefully that's enough.

Even Elven eyesight can't track the fight further; both parties to it are moving fast, now, or not moving at all, the nature of the fight makes those hard to tell apart -

By rights the dragon should be the single most conspicuous thing on the continent. Nope.

Aside from the strategic value, does the oath come into play on this? There's some hoarding going on here, but it's definitely not an Elf or Maia doing it...

There's a or-anything-else clause but it doesn't look like pursuit is actionable.

Then the end result is just that the Enemy's down a Silmaril.
At least until your cousins figure out a way to track it, at which point we have to work out how to fight a dragon.