Marath, Will of the Wild + Cathars' Crusade + Crystalline Crawler + Doubling Season
Marath, Will of the Wild
Cathars' Crusade
Crystalline Crawler
Doubling Season
Infinite colored manaInfinite creature tokensInfinite damageInfinite death triggersInfinite creature ETBInfinite creature LTBInfinite creature tokens that are infinitely largeInfinite +1/+1 counters on creatures you control
How it works
Activate Marath by paying 1, creating two 1/1 Elemental tokens.
Cathars' Crusade triggers twice, putting four +1/+1 counter to all creatures you control.
Activate Crystalline Crawler by removing a +1/+1 counter from it, adding 1.
Repeat.
This engine transforms Marath, Will of the Wild into an unstoppable force by letting its activated ability feed right back into itself, supercharged by Doubling Season to generate a surplus of counters and tokens. Every time Marath pays one mana to create an Elemental, Doubling Season doubles the tokens and Cathars' Crusade ensures that all your creatures—including Marath and Crystalline Crawler—receive an avalanche of +1/+1 counters. You can then siphon counters off Crystalline Crawler for mana to sustain the loop while it continuously grows alongside the rest of your board.