Part 5

At the same time, there is talk about black boxes. Far Madding too is „shown“ and even said (!) to be one such box:

„It’s over, Rand,” Min said gently, moving her sturdy brown mare nearer to his gray gelding, though she already stayed as close to him as Nynaeve did to Lan. Lan’s bruises, and a broken arm, had been Healed before she had attended to Rand. Min’s face reflected the worry flowing through the bond. Letting her cloak go on the wind, she patted his arm. “You don’t have to think about it anymore.”

“I’m grateful to Far Madding, Min.” His voice was emotionless, distant, as it had been when he seized saidin in the early days. He would have warmed it for her, but that seemed beyond him. “I really did find what I needed here.” If a sword had memory, it might be grateful to the forge fire, but never fond of it. “

Such a black box is probably another expression for an „endless nightmare“.
And also, one such a black box is „seen“ by Perrin when he climbs up Dragonmount in the dreamworld. Inside, Rand is reliving LTT’s memories (probably several times). And then there is ofc the „Trap“ in TGH:

„Rand stepped inside.Blink.A smiling, bald-headed man in rough clothes laid a slice of meat on a plate held by a woman with a worn face (…) That door burst open, and—Blink.Rand could not move. The flies buzzing over the table sounded louder. His breath made a cloud in front of his mouth.“

„Blink. A smiling, bald-headed man(…)“ „That door burst open, and—Blink.Rand struggled, but his muscles seemed frozen. The room was colder; he wanted to shiver, but he could not move even that much. Flies crawled all over the table. He groped for the void. The sour light was there, but he did not care. He had to—Blink.A smiling, bald-headed (…) „That door burst open, and—Blink.The room was freezing. So cold. Flies blackened the table; the walls were a shifting mass of flies, the floor, the ceiling, all black with them. They crawled on Rand, covering him, crawled over his face, his eyes, into his nose, his mouth. Light, help me. Cold. The flies buzzed like thunder. Cold. It penetrated the void, mocking the emptiness, encasing him in ice. Desperately he reached for the flickering light. His stomach twisted, but the light was warm. Warm. Hot. He was hot. Suddenly he was tearing at . . . something. He did not know what, or how. Cobwebs made of steel. Moonbeams carved from stone. They crumbled at his touch, but he knew he had not touched anything. They shriveled and melted with the heat that surged through him, heat like a forge fire, heat like the world burning, heat like—It was gone. Panting, he looked around with wide eyes. A few flies lay on the half-carved roast, in the platter. Dead flies. Six flies. Only six.“