My theory explains how the Seals on the Dark One’s prison can be breaking when they are made with something supposedly unbreakable. The Seals that are the focal points to the Sealing of the Bore are made of cuendillar:
Seven indestructible cuendillar disks, made with the One Power and marked with the seal of the Aes Sedai, were prepared to function as ‘focus points’.They were made by men and women prior to the attack on Shayol Ghul before the female Aes Sedai decided to take no part in the attack to reseal the Dark One in the Bore.
- Robert Jordan’s The Wheel of Time
Lost during the Trolloc Wars, the Seals have been gradually found. Some, like the one at the Eye of the World, have been found already broken, others, such as the one Taim brought Rand, have been found intact. The one Elayne and Nynaeve found in Tanchico was originally intact, but broke on the way to Salidar. When a Seal is about to break, it feels filthy and evil:
Evil seemed to bathe her hand, stronger than ever, as if the Dark One really was trying to break through the cuendillar seal.Interestingly, the Seal at the Eye was found broken, yet when Lan tried to cut it, his blade broke. However, Morvrin broke one fragment of the Tanchico Seal with her hands in The Fires of Heaven. Therefore the later breaking Seal was more fragile than the first Seal to break. More on this anon.
- The Fires of Heaven, Leavetakings.
Until Egwene rediscovered how,
no one has been able to make cuendillar since the Age of Legends. And even then it was made only for the greatest purpose. Once made, nothing can break it. Not the One Power itself wielded by the greatest Aes Sedai who ever lived aided by the most powerful sa’angreal ever made. Any power directed against it only makes it stronger.Since cuendillar is made with the One Power, and can’t be broken by using force on it, perhaps the reverse is true.
- The Eye of the World, There Is Neither Beginning Nor End
My theory is that cuendillar is weakened when the One Power is withdrawn or absorbed out of it, and this is why the Seals are crumbling.
The Dark One is the only being with the skill, strength and motivation to do this. He can feel the Seals (the focus points) from within his prison and has very gradually absorbed the One Power out of five of them in turn.
The feel of evil sensed while the Seals are weakening, but not afterward, supports this.
”It [the Seal] was whole when we put it in the purse.” Nynaeve paused to work moisture back into her mouth…Once the Seal breaks the feeling of evil is gone. Therefore the evil sensed was not the feel of the Dark One in his prison in the Bore, because that would have remained in the fragments, and so far in the books has only been felt in the Bore. It was the feel of the Dark One doing something to the Seal – actively weakening it. With his increased ability to touch the World, the later Seals have more of the Power leached out of them, and so are more fragile. That is why Morvrin broke the Tanchico fragment with her hands, but Lan’s steel knife broke on the Eye of the World fragment.
“We didn’t look at it,” Elayne said breathlessly, “or touch it more than we had to. It felt filthy, evil.” It no longer did.
- The Fires of Heaven, To Teach and To Learn.
The feel of evil as the Seal weakens is the last stages of the Dark One weakening the cuendillar by absorbing the One Power out of it. And cuendillar crumbles…