Aether Storm + Mindslaver + Valley Floodcaller

Aether Storm

Mindslaver

Valley Floodcaller

How it works

1. Activate Mindslaver by paying 4 and tapping it, causing you to gain control of target opponent during their next turn.
2. During the opponent's turn, cast Aether Storm by paying 3.
3. As the opponent, activate Aether Storm by paying 4 life.
4. Repeat step 3 until the opponent has 3 or less life remaining.