Declare Lord Xander as an attacker, triggering its ability, causing an opponent to mill a number of cards equal to half their library, rounded down, times two due to Bruvac.

Infinite mill for target opponent

Bruvac the Grandiloquent

Lord Xander, the Collector

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.

Fraying Sanity

Declare Lord Xander as an attacker, triggering its second ability, causing the defending player to mill half their library, rounded down.
Activate Keening Stone by paying {5} 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.

Keening Stone

Declare Lord Xander as an attacker, triggering its second ability, causing the defending player to mill half their library, rounded up.
Activate Consuming Aberration by tapping it, causing the opponent to mill cards equal to the cards in opponents' graveyards, milling the remainder of their library.

Phenax, God of Deception

Consuming Aberration

Declare Lord Xander as an attacker, triggering its ability, causing an opponent to mill half their library, rounded down.
Activate Riverchurn Monument's exhaust ability by paying {2}{U}{U} and tapping it, causing each player to mill cards equal to the number of cards in their graveyard.

Riverchurn Monument

Declare Lord Xander as an attacker attacking the opponent named by Sewer Nemesis. Lord Xander's second ability triggers, causing the opponent to mill half their library, rounded up.
Activate Sewer Nemesis by tapping it, causing the opponent to mill cards equal to the cards in their graveyard, milling the remainder of their library.

Combos with "Lord Xander, the Collector"