Shaun, Father of Synths, and Aurelia, the Warleader

Prerequisites

• Shaun, Father of Synths on the battlefield
• Aurelia, the Warleader on the battlefield

Steps

1. Declare Aurelia as an attacker, triggering it and Shaun's first ability
2. Resolve the Shaun trigger, creating a tapped and attacking copy of Aurelia that is a nonlegendary Synth in addition to its other types
3. Resolve the Aurelia trigger, untapping all creatures you control and causing you to get an additional combat phase after this one
4. Repeat each combat phase

Results

• Infinite combat phases
• Infinite creature tokens with haste
• Infinite ETB
• Infinite mana creatures you control can produce
• Infinite untap of creatures you control