Requires

Marath, Will of the Wild must be on the battlefield. Mana Echoes must be on the battlefield. Pir, Imaginative Rascal must be on the battlefield. Marath has at least three +1/+1 counters on it. Mana needed:

Steps

1. Activate Marath by paying and removing a +1/+1 counter from it, creating a 1/1 Elemental creture token.
2. The Elemental enters the battlefield, triggering Mana Echoes, adding for each Elemental you control.
3. Activate Marath by paying and removing a +1/+1 counter from it, putting two +1/+1 counters on it.
4. Repeat.
5. Once you have infinite , you may repeat step 3 to give Marath infinite +1/+1 counters, then use them to deal infinite damage to any target(s).

Results