Why Capture the Seals?

Question

Background

I finished the series several years ago, and I am now listening through it again. I just re-completed the fourth book, and the sequence that made me ask this question of myself is when:

Nynaeve goes toe-to-toe with Moghedien in the Panarch's palace. It seems to me she took on considerable extra risk to secure the seal.

At the end of the very first book:

Moiraine finds a broken seal at the bottom of the Eye of the World.

Inferences

This early discovery implies (to me at least) that the seals can be broken purely by the Dark One's influence, with no outside intervention. No one at the time (or even by the end of the fourth book) has reached any sort of conclusion that they are weakening, let alone that they can be broken by any normal means.

It is understandable that they wouldn't want to explore the subject in great detail; accidentally breaking one could have disastrous consequences. But based on the information available, there is virtually nothing they can do to protect them either. Perhaps the Forsaken know more about how they can be destroyed/protected, but certainly not anyone on the side of the Light.

Question

Several times in the WoT series, the protagonists and antagonists alike make concerted efforts to secure the seals in their possession. Why?

Answer 1

Because it's the prudent thing to do.

By the end of The Eye of the World, the 'good guys' know that it's possible to break the seals. Of course it should be impossible to break cuendillar, but since it's happened once, all bets are off: perhaps the seals are now as fragile as Sea Folk porcelain (as later turns out to be the case). At any rate, they're not as unbreakable as they should be, and therefore worth keeping safe.

The seals are also incredibly important. They're what's keeping the Dark One bound in his prison; if they break, the world could come to an end and the Pattern could be broken. It's worth going to a lot of trouble to protect them, even just on the off-chance that they might be breakable by normal means.

Let's have an analogy: imagine you're hanging from a steel cable on the side of a cliff. Although the cable is meant to be pretty much unbreakable, you've just seen another one snap like thin cotton and you don't know why. You're going to want to be pretty damn careful with the one you're hanging from, not subject it to any unnecessary stress, do all you can to protect it from any possible harm.

As for the 'bad guys', the Forsaken and so on, perhaps some of them know exactly what to do to break the seals once they get hold of them. If they're getting instructions directly from the Dark One, we can consider them better informed than most of our heroes. Even if Rand and co. don't know for sure how fragile the seals are now, the Forsaken may well know.

Not only that, but the 'good guys' are probably smart enough to realise this, which gives them even more incentive to keep the seals out of enemy hands. If breaking the seals would be a worldwide calamity, and also possible (even if you don't yet know how), then letting even one of them fall into the clutches of people who want them broken would be an exceptionally bad idea.

Answer 2

To answer the edit.

By the end of the first book like you said, they find a broken seal, something that should be impossible. They now know the seals can be broken, if they don't nessesarily know how. At best they know that Dark One isn't able to break them all immediately, since some are still intact. Like my original answer states, the reason the "good guys" are after the seals is to keep them away from the Forsaken. While the Forsaken may not be able to break them personally, they could at least take them to Shayol Ghul where the Dark One can exert far more power and break the seals faster. Again at the end of the day, the point of holding onto the seals is so that the "good guys" can "attempt" at least to delay the destruction of the other seals.

In the end we know that the "good guys" plan pays off, as they are able to destroy the seals themselves, right when Rand needs them to, so he can re-seal the Dark One. 3 seals make it almost 4 years after the events of the first book.

Original answer.

The seals are weakened due to the taint of the Dark One, and by the end of the series are able to be snapped in half in your hands.

Whoever controls the seals controls when they will be broken to release the Dark One, or not broken to keep the Dark One sealed.

Moiraine shows us in The Fires of Heaven how weak they are already by book 5:

Drawing her belt knife, its hilt wrapped in silver wire, Moiraine scraped delicately at the edge of the disc. And a tiny flake of solid black fell away.

That flake lying on the table was impossible. Those discs were made of cuendillar, heartstone, and nothing made of cuendillar could be broken, not even by the One Power. Whatever force was used against it only made it stronger. The making of heartstone had been lost in the Breaking of the World, but whatever had been made of it during the Age of Legends still existed, even the most fragile vase, even if the Breaking had sunk it to the bottom of the ocean or buried it beneath a mountain. Of course, three of the seven discs were broken already, but it had taken a good deal more than a knife.