Agatha's Soul Cauldron, Siren of the Silent Song, and Fatestitcher

Prerequisites

• Agatha's Soul Cauldron on the battlefield
• Siren of the Silent Song on the battlefield
• Fatestitcher in exile

Steps

1. Activate Siren of the Silent Song using Fatestitcher's ability by tapping it, untapping another creature you control that has a +1/+1 counter on it
2. Activate the other creature using Fatestitcher's ability by tapping it, untapping Siren of the Silent Song Siren of the Silent Song triggers, causing each opponent to discard and mill a card
3. Repeat

Results

• Infinite mill