Omarthis, Ghostfire Initiate + Mirage Mirror + Forsaken Monument + Mirror Gallery

Omarthis, Ghostfire Initiate

Mirage Mirror

Forsaken Monument

Mirror Gallery

How it works

1. Put a +1/+1 counter on a colorless creature you control.
2. Omarthis's first triggered ability triggers.
3. In response, activate Mirage Mirror by paying 2, causing it to become a copy of Omarthis until end of turn.
4. Resolve the Omarthis trigger, putting a +1/+1 counter on itself.
5. Mirage Mirror triggers, putting a +1/+1 counter on itself.
6. Omarthis triggers, putting a +1/+1 counter on itself.
7. Repeat from step 5 any number of times.
8. End the loop by declining to place a +1/+1 counter on a creature.
9. Warning: Omarthis's last ability can increase the risk of losing by drawing from an empty library if you place enough counters on them.

This clever loop transforms Mirage Mirror into a copy of Omarthis, Ghostfire Initiate, letting the two mutually trigger each other into an ever-growing avalanche of counters. Because Mirror Gallery is on the battlefield, the legendary rule won't get in your way as the copies proliferate, while Forsaken Monument supercharges your colorless mana base to easily pay for the Mirror's activations. You can safely repeat this stacking effect as many times as you like, ultimately leaving your creatures overwhelmingly massive—just be careful not to trigger Omarthis's death ability with too many counters later, or you might manifest your entire library into the graveyard!