Blossoming Tortoise + Crackdown Construct + Blinkmoth Nexus

Blossoming Tortoise

Crackdown Construct

Blinkmoth Nexus

How it works

1. Activate Blinkmoth Nexus's second ability by paying 0, causing it to become a 1/1 Blinkmoth creature in addition to its other types until end of turn.
2. Activate Blinkmoth Nexus's second ability by paying 0.
3. Crackdown Construct triggers, giving itself +1/+1 until end of turn.
4. Repeat from step 2.

This elegant engine centers around Crackdown Construct, which grows massively each time you activate a non-mana ability of an artifact or creature. While Blinkmoth Nexus is normally a modest land, its animation ability can be activated repeatedly for zero mana thanks to Blossoming Tortoise's passive cost reduction, which shaves the activation price down from one mana to nothing. Every single one of these zero-cost activations safely triggers Crackdown Construct over and over again, rapidly pumping it into an infinitely large creature ready to swing for the win.