Blue Mill Control with Drowned Secrets for Commander

Drowned Secrets mills the opponent whenever you cast a blue spell, while Thassa's Oracle allows you to win the game if you have no cards left in your library. This creates a win condition that can be achieved through milling.

Both of these cards are powerful mill spells. Glimpse the Unthinkable mills 10 cards, and Traumatize mills half of the opponent's library. Together, they can quickly reduce the opponent's library to zero cards, setting up for a win with Thassa's Oracle or Jace, Wielder of Mysteries.

Psychic Corrosion triggers whenever you draw a card, milling the opponent for 1 for each card drawn. Opt allows you to filter through your deck while also drawing a card, synergizing with Psychic Corrosion to mill your opponent further.

Jace provides a win condition if you have no cards left in your library, while Blue Sun's Zenith can draw you a large number of cards, thereby milling your opponent more effectively. If you use Blue Sun's Zenith to draw your entire library, you can then activate Jace to win the game.

Merfolk Mesmerist can tap to mill an opponent when it enters the battlefield, while Mental Note allows you to mill a card and draw a card. Together, they provide a low-cost way to further mill your opponent's library while cycling through your own cards.