Emptiness + Phyrexian Altar + Skullwinder

Emptiness

Phyrexian Altar

Skullwinder

How it works

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 Skullwinder from your graveyard to the battlefield.
6. When Skullwinder enters, it triggers, returning Emptiness from your graveyard to your hand.
7. Activate Phyrexian Altar by sacrificing Skullwinder, adding .
8. Repeat.

This ingenious loop relies on turning Emptiness's self-sacrificing evoke drawback into an engine by intercepting it with Phyrexian Altar. When you cast Emptiness for its evoke cost using white mana, its entry triggers both a graveyard-reanimation effect and its forced sacrifice, but sacrificing it to Phyrexian Altar first puts the creature safely in the graveyard while producing the mana needed to keep going. The reanimation ability then pulls Skullwinder out of your graveyard, whose own entry trigger plucks Emptiness right back to your hand. Finally, sacrificing Skullwinder to Phyrexian Altar resets the loop, allowing you to endlessly recur your threats while giving your opponents cards back in the process.