Scouring Swarm + Drownyard Temple + Phyrexian Altar + Trenching Steed

Scouring Swarm

Drownyard Temple

Phyrexian Altar

Trenching Steed

How it works

1. Activate Trenching Steed by sacrificing Drownyard Temple.
2. Each Scouring Swarm you control triggers, creating a tapped token copy of itself.
3. Resolve the Trenching Steed ability.
4. If you control four or more Scouring Swarms, activate Phyrexian Altar by sacrificing a Scouring Swarm, adding 1.
5. Repeat step 4 until you control three Scouring Swarms or until you have 3 available, whichever comes first.
6. Activate Drownyard Temple by paying 3, returning it from your graveyard to the battlefield.
7. Repeat.

This clever loop hinges on the synergy between Trenching Steed and Drownyard Temple, where the land is repeatedly fed to the Steed's sacrifice ability to fund its own resurrection. Once your graveyard fills up with enough land cards, Scouring Swarm takes advantage of those land sacrifices to rapidly multiply your token army whenever the condition is met. With your forces swelling, Phyrexian Altar steps in to convert the excess creature tokens into the mana required to activate Drownyard Temple and keep the cycle spinning infinitely.