Blossoming Tortoise + Crackdown Construct + Mutavault

Blossoming Tortoise

Crackdown Construct

Mutavault

How it works

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

This clever loop turns a modest land into an infinitely massive threat by exploiting a cost-reduction engine. With Blossoming Tortoise on the board, the activation cost of Mutavault's self-animation ability is discounted to zero mana, allowing you to activate it repeatedly without draining your resources. Every time you pull off this zero-cost activation, Crackdown Construct notices and triggers its ability, continuously stacking +1/+1 bonuses onto itself to grow to arbitrary size.