Sprout Swarm + Pitiless Plunderer + Phyrexian Altar + Primal Vigor

Sprout Swarm

Pitiless Plunderer

Phyrexian Altar

Primal Vigor

How it works

1. Cast Sprout Swarm with buyback by paying 4, creating two 1/1 Saproling creature tokens.
2. Activate Phyrexian Altar twice by sacrificing the Saprolings, adding 1.
3. When the Saprolings die, Pitiless Plunderer triggers twice, creating four Treasure artifact tokens.
4. Activate three Treasures by tapping and sacrificing them, adding 3.
5. Repeat.
6. Once you have infinite Treasure tokens and colored mana, you may forego sacrificing the Saproling tokens.

This clever loop turns a modest green instant into an unstoppable token engine by exploiting a clever synergy of multipliers and mana-returns. When you cast Sprout Swarm with its buyback cost, Primal Vigor doubles the resulting Saproling tokens, which can then be fed directly into Phyrexian Altar and leveraged through Pitiless Plunderer's death triggers to generate an excess of Treasure tokens and mana. Because Sprout Swarm's convoke and buyback costs are more than completely offset by the sacrificed creatures and amassed Treasures, you can endlessly repeat the process—eventually leaving you with an infinite supply of creatures, artifacts, and colored mana.