Urza, Prince of Kroog + Training Grounds + Encroaching Mycosynth + Earthcraft

Urza, Prince of Kroog

Training Grounds

Encroaching Mycosynth

Earthcraft

How it works

1. Activate the basic land by tapping it, adding 1.
2. Activate Urza by paying 4, creating a token copy of Training Grounds that is a 1/1 Soldier in addition to its other types.
3. Activate Earthcraft by tapping the Training Grounds token, untapping a basic land.
4. Activate the basic land by tapping it, adding 1.
5. Activate Urza by paying 2, creating a token copy of Training Grounds that is a 1/1 Soldier in addition to its other types.
6. Activate Earthcraft by tapping the Training Grounds token, untapping a basic land.
7. Activate the basic land by tapping it, adding 1.
8. Activate Urza by paying 1, creating a token copy of Training Grounds that is a 1/1 Soldier in addition to its other types.
9. Repeat from step 6.

This elegant loop relies on Encroaching Mycosynth to turn Training Grounds into an artifact, allowing Urza, Prince of Kroog to copy it while Earthcraft provides the necessary untap utility to fuel the engine. Because Training Grounds reduces the activation cost of Urza's ability, each successive copy of Training Grounds progressively discounts the cost to make the next one. Once the cost reduction bottoms out at one mana, Earthcraft easily offsets that single mana investment by untapping a basic land, allowing you to flood the battlefield with an endless parade of creature tokens.