Nethroi, Apex of Death + Phyrexian Altar + Mitotic Slime + Cavern Harpy

Nethroi, Apex of Death

Phyrexian Altar

Mitotic Slime

Cavern Harpy

How it works

1. Cast Nethroi either from your hand or from the command zone for its mutate cost by paying 4G/W, putting it under a non-Human creature you control.
2. Nethroi triggers, returning Cavern Harpy and Mitotic Slime from your graveyard to the battlefield.
3. When Cavern Harpy enters, it triggers, returning Nethroi from the battlefield to your hand.
4. Activate Phyrexian Altar twice by sacrificing Cavern Harpy and Mitotic Slime, adding .
5. When Mitotic Slime dies, it triggers, creating two 2/2 Ooze creature tokens.
6. Activate Phyrexian Altar twice by sacrificing the Oozes, adding 1G/W.
7. When the Oozes die, they trigger, creating four 1/1 Ooze creature tokens.
8. Activate Phyrexian Altar three times by sacrificing three Oozes, adding 3.
9. Repeat.

This ingenious loop turns Nethroi, Apex of Death into a devastating recursion engine by exploiting its mutate trigger to pull both Cavern Harpy and Mitotic Slime directly from your graveyard. Once those pieces are on the board, Cavern Harpy bounces Nethroi back to your hand so it can be mutated all over again, while Phyrexian Altar provides the mana needed to sustain the loop by sacrificing creatures. As Mitotic Slime dies and cascades down into its 2/2 and 1/1 Ooze tokens, the Altar greedily consumes every last one of them to generate a surplus of colored mana and an endless tide of sacrifices.