Emptiness, Phyrexian Altar, and Eternal Witness

Prerequisites

• Emptiness in hand
• Phyrexian Altar on the battlefield
• Eternal Witness in the graveyard
• available

Steps

1. Cast Emptiness for its evoke cost by paying
2. When Emptiness enters, its first ability and evoke ability trigger
3. Holding priority, activate Phyrexian Altar by sacrificing Emptiness, adding
4. Resolve Emptiness's evoke trigger, failing to sacrifice it as it's no longer on the battlefield
5. Resolve Emptiness's first trigger, returning Eternal Witness from your graveyard to the battlefield
6. When Eternal Witness enters, it triggers, returning Emptiness from your graveyard to your hand
7. Activate Phyrexian Altar by sacrificing Eternal Witness, adding
8. Repeat

Results

• Infinite LTB
• Infinite ETB
• Infinite sacrifice triggers
• Infinite death triggers
• Infinite storm count