Omarthis, Ghostfire Initiate + Mirage Mirror + Instruments of War + Mirror Gallery

Omarthis, Ghostfire Initiate

Mirage Mirror

Instruments of War

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 hinges on Mirage Mirror temporarily becoming a copy of Omarthis, Ghostfire Initiate, allowing the two legendary elementals to constantly trigger each other's growth whenever a +1/+1 counter is placed. While Mirror Gallery ensures you don't lose your copy to the legend rule, the passive lord bonus from Instruments of War ensures your evolving entities stay distinct and properly pumped. You can feed this escalating cycle as many times as you like to grow your board infinitely, though you'll want to watch out before converting all those counters into a massive pile of manifested cards when Omarthis eventually meets its demise!