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

Prerequisites

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

Steps

1. Activate Siren of the Silent Song using Kelpie Guide's ability by tapping it, untapping another creature you control that has a +1/+1 counter on it
2. Activate the other creature using Kelpie Guide'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