Lord Xander, the Collector + Keening Stone

Prerequisites

—

Steps

1. 1Declare Lord Xander as an attacker, triggering its second ability, causing the defending player to mill half their library, rounded down.
2. 2Activate Keening Stone by paying and tapping it, causing the player to mill cards equal to the number of cards in their graveyard, thus milling the rest of their library.

Effects

• Infinite mill for target opponent