Cast Maddening Cacophony with kicker by paying {4}{U}{U}, causing each opponent to mill their library due to Bruvac.

Infinite mill

Bruvac the Grandiloquent

Maddening Cacophony

Cast Maddening Cacophony with kicker by paying {4}{U}{U}, causing each opponent to mill cards equal to half their library size, rounded up.
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.

Infinite mill for target opponent

Near-infinite mill

Fraying Sanity

Cast Maddening Cacophony with kicker by paying {4}{U}{U}, causing each opponent to mill half their library, rounded up.
Activate Riverchurn Monument's exhaust ability by paying {2}{U}{U} and tapping it, causing each opponent to mill the remainder of their library.

Riverchurn Monument

Activate Duskmantle Guildmage's first ability by paying {1}{U}{B}.
Cast Maddening Cacophony with kicker by paying {4}{U}{U}, causing each opponent to mill half their library, rounded up.
Duskmantle Guildmage triggers for each card milled this way.
Resolve the first Duskmantle Guildmage trigger, causing the opponent to lose 1 life.
Repeat step 4 until the opponent loses the game due to having zero or less life.
Repeat from step 4 for each remaining trigger.

Each opponent loses the game

Near-infinite lifeloss

Duskmantle Guildmage

Cast Maddening Cacophony with kicker by paying {4}{U}{U}, causing each opponent to mill half their library, rounded up.
Activate Consuming Aberration by tapping it, causing a opponent to mill cards equal to the cards in opponents' graveyards, milling the remainder of their library.

Phenax, God of Deception

Consuming Aberration

Cast Maddening Cacophony with kicker by paying {4}{U}{U}, causing each opponent to mill half their library, rounded up.
Activate Keening Stone by paying {5} and tapping it, causing an opponent to mill cards equal to the number of cards in their graveyard, thus milling the rest of their library.

Keening Stone

Cast Maddening Cacophony with kicker by paying {4}{U}{U}, causing the opponent named by Sewer Nemesis 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.

Sewer Nemesis

Cast Doomsday Excruciator by paying {B}{B}{B}{B}{B}{B}.
When Doomsday Excruciator enters, it triggers, causing each player to exile all but the bottom six cards of their library.
Cast Maddening Cacophony by paying {1}{U}, causing each opponent to mill the rest of their library.

Combos with "Maddening Cacophony"