Those wound tightest are first to unravel.

Fraying Sanity

Enchant player
At the beginning of each end step, enchanted player mills X cards, where X is the number of cards put into their graveyard from anywhere this turn.

"The king! The king has been murdered! It is regicide! Vault Boy... what did you do? What did... *we* do?"

Fallout

"I saw my mind stretch like cloth on a loom,
Warping, twisting toward a deathless doom."
—*A Traveler's Trials*

Wilds of Eldraine: Enchanting Tales

Fraying Sanity's triggered ability counts the number of cards that were put into the enchanted player's graveyard during the turn, even if Fraying Sanity wasn't on the battlefield at the time those cards were put there, and even if those cards have left that graveyard.

The value of X is determined only as Fraying Sanity's triggered ability resolves. For example, if three Fraying Sanity Auras are attached to one player who had four cards put into their graveyard this turn, X will be four for the first ability to resolve, eight for the second, and sixteen for the third.