Helm of Obedience, and Leyline of the Void

Prerequisites

• Helm of Obedience on the battlefield
• Leyline of the Void on the battlefield
• available

Steps

1. Activate Helm of Obedience by paying and tapping it, causing target opponent to mill a card
2. Due to Leyline of the Void's replacement effect, the milled card is exiled instead of going to the graveyard, and that opponents repeats that process until their library is empty

Results

• Exile target opponent's library