Gilder Bairn + Crystalline Crawler + Earthcraft

Gilder Bairn

Crystalline Crawler

Earthcraft

How it works

1. Activate a basic land by tapping it, adding 1.
2. Activate Earthcraft by tapping Gilder Bairn, untapping the basic land.
3. Activate the basic land by tapping it, adding 1.
4. Activate Gilder Bairn by paying 2G/U and untapping it, doubling each counter on Crystalline Crawler.
5. Activate Crystalline Crawler's first ability twice by removing two +1/+1 counters from it, adding 1G/U.
6. Repeat from step 2.
7. Once you have infinite +1/+1 counters on Crystalline Crawler, you may instead double the counters on any other permanent(s).

This clever loop turns Crystalline Crawler into a self-sustaining mana battery, using its ability to convert its own +1/+1 counters into the exact colors needed to fund Gilder Bairn's untap cost. Earthcraft serves as the crucial bridge, letting you tap Gilder Bairn to effortlessly untap a basic land without needing to spend actual mana on the activation. Once Gilder Bairn uses its untap symbol to double Crystalline Crawler's counters rather than itself, the exponential growth quickly spirals out of control.