The Thirteenth Doctor, and Gogo, Master of Mimicry

Prerequisites

• The Thirteenth Doctor on the battlefield
• Gogo, Master of Mimicry on the battlefield

Steps

1. At the beginning of your end step, The Thirteenth Doctor triggers
2. Holding priority, activate any number of creatures you control that have counters on them by tapping them, adding at least
3. Activate Gogo by paying and tapping it, copying The Thirteenth Doctor's trigger
4. Resolve the copy of The Thirteenth Doctor's trigger, untapping all creatures you control that have a counter on them
5. Repeat from step 2

Results

• Infinite mana creatures you control with counters on them can produce
• Infinite untap of creatures you control with counters on them