Crackdown Construct, and Umbral Mantle

Prerequisites

• Crackdown Construct on the battlefield
• Umbral Mantle on the battlefield

Steps

1. Activate Umbral Mantle's ability targeting Crackdown Construct
2. Crackdown Construct gets +1/+1 until end of turn
3. Repeat

Results

• Infinitely large Crackdown Construct