Cathars' Crusade, Barrenton Medic, and Presence of Gond

Prerequisites

• Cathars' Crusade on the battlefield
• Barrenton Medic on the battlefield
• Presence of Gond on the battlefield
• Presence of Gond attached to Barrenton Medic
• Barrenton Medic does not have summoning sickness

Steps

1. Activate Barrenton Medic by tapping it, creating a 1/1 Elf Warrior creature token
2. The Elf Warrior enters the battlefield, triggering Cathars' Crusade, putting a +1/+1 counter on each creature you control
3. Activate Barrenton Medic's second ability by putting a -1/-1 counter on it, untapping it
4. Repeat

Results

• Infinite creature tokens
• Infinite ETB
• Infinite +1/+1 counters