Progenitor Mimic, and Felidar Guardian

Prerequisites

• Progenitor Mimic in hand
• Felidar Guardian on the battlefield

Steps

1. Cast Progenitor Mimic by paying its mana cost, choosing to have it enter the battlefield as a copy of Felidar Guardian When Progenitor Mimic enters the battlefield, it triggers, blinking Felidar Guardian
2. When Felidar Guardian enters the battlefield, it triggers, blinking Progenitor Mimic
3. Choose to have Progenitor Mimic enter the battlefield as a copy of Felidar Guardian
4. Repeat from step 2

Results

• Infinite LTB
• Infinite ETB