Toph, Greatest Earthbender + Power Depot + Crystalline Crawler + Phantom Train + Brad Boimler, Eager Ensign

Toph, Greatest Earthbender

Power Depot

Crystalline Crawler

Phantom Train

Brad Boimler, Eager Ensign

How it works

1. Play Power Depot, which will enter with a +1/+1 counter on it due to its modular ability
2. Cast Toph either from your hand or from the command zone by paying 2 plus commander tax if applicable.
3. When Toph enters, it triggers, earthbending Power Depot and putting a number of +1/+1 counters on Power Depot equal to the mana spent to cast Toph, increased by Brad Boimler.
4. Activate Phantom Train by sacrificing Power Depot.
5. When Power Depot dies, its modular ability and Toph trigger.
6. Resolve the modular trigger, putting the +1/+1 counters that were on Power Depot onto Crystalline Crawler, increased by Brad Boimler.
7. Resolve the Toph trigger, returning Power Depot from your graveyard to the battlefield tapped. Power Depot will enter with a +1/+1 counter on it due to its modular ability
8. Resolve the Phantom Train ability.
9. Activate Phantom Train by sacrificing Toph. Choose to return Toph from your graveyard to the command zone.
10. Activate Crystalline Crawler by removing a +1/+1 counter from it, adding R/G.
11. Repeat step 10 until you have enough mana to cast Toph.
12. Repeat from step 2.

This intricate loop relies on amplifying and recycling counters to generate an unstoppable engine of infinite resources. When Toph, Greatest Earthbender enters the battlefield, her earthbend ability is supercharged by Brad Boimler, Eager Ensign to flood Power Depot with a massive hoard of counters. You then sacrifice Power Depot to Phantom Train, triggering both modular and Toph's ability to seamlessly return the land to the battlefield ready to be sacrificed again. Meanwhile, Crystalline Crawler acts as your mana battery, turning the growing collection of +1/+1 counters into the exact colored mana needed to repeatedly recast Toph from the command zone and keep the cycle spinning infinitely.