Lord Xander and Fraying Sanity on the battlefield.
Fraying Sanity attached to an opponent with an even library size.
Lord Xander does not have summoning sickness.
Steps
Declare Lord Xander as an attacker, attacking the opponent enchanted by Fraying Sanity.
Lord Xander's second ability triggers, causing the opponent to mill cards equal to half their library size, rounded down.
At the beginning of your end step, Fraying Sanity triggers, causing the opponent enchanted by Fraying Sanity to mill cards equal to the number of cards put into their graveyard this turn.