They have no Aes Sedai touching the True Source to protect them. Blacksmith, perhaps the walls have weakened enough for the Dark One himself to touch events. Not with a free hand, or we’d be done already, but maybe tiny shiftings in the threads. A chance turning of one corner instead of another, a chance meeting, a chance word, or what seems like chance, and they could be so far under the Shadow not even Moiraine could bring them back.