Polyraptor, Forerunner of the Empire, and Cathars' Crusade

Prerequisites

• Polyraptor on the battlefield
• Forerunner of the Empire on the battlefield
• Cathars' Crusade on the battlefield
• You have a way to deal damage to Polyraptor

Steps

1. Deal damage to Polyraptor
2. Polyraptor triggers, creating a token copy of it
3. The Polyraptor token enters the battlefield, triggering Forerunner of the Empire's second ability and Cathars' Crusade
4. Resolve the Cathars' Crusade trigger, putting a +1/+1 counter on each creature you control
5. Resolve the Forerunner of the Empire trigger, dealing 1 damage to each creature
6. Each Polyraptor you control triggers
7. Resolve a Polyraptor trigger, creating a token copy of it
8. Repeat from step 3

Results

• Infinite +1/+1 counters
• Infinite creature tokens
• Infinite damage to all creatures
• Infinite damage to creatures
• Infinite death triggers
• Infinite ETB
• Infinite LTB