Riverchurn Monument, and Terisian Mindbreaker

Prerequisites

• Riverchurn Monument on the battlefield
• Terisian Mindbreaker on the battlefield
• undefined available

Steps

1. Declare Terisian Mindbreaker as an attacker, triggering its ability, causing an opponent to mill half their library, rounded up
2. Activate Riverchurn Monument's exhaust ability by paying and tapping it, causing each player to mill cards equal to the number of cards in their graveyard, thus causing the player attacked by Terisian Mindbreaker to mill the rest of their library

Results

• Infinite mill for target opponent