Riverchurn Monument + Fleet Swallower

Riverchurn Monument

Fleet Swallower

How it works

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