Crackdown Construct, and Umbral Mantle

Prerequisites

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

Steps

1. Activate Umbral Mantle's equip ability by paying
2. Crackdown Construct triggers, giving it +1/+1 until end of turn
3. Resolve Umbral Mantle's equip ability
4. Repeat

Results

• Infinitely large Crackdown Construct until end of turn