Ghave, Guru of Spores, Devoted Druid, and Cathars' Crusade

Prerequisites

• Ghave, Guru of Spores on the battlefield
• Devoted Druid on the battlefield
• Cathars' Crusade on the battlefield
• Ghave has at least two +1/+1 counters on it, or there is a +1/+1 counter on another creature you control
• Devoted Druid does not have summoning sickness

Steps

1. Activate Devoted Druid's first ability by tapping it, adding
2. Activate Ghave's first ability by paying and removing a +1/+1 counter from a creature you control, creating a 1/1 Saproling creature token
3. When the Saproling enters the battlefield, Cathars' Crusade triggers, putting a +1/+1 counter on each creature you control
4. Activate Devoted Druid's second ability by putting a -1/-1 counter on it, untapping it
5. Repeat

Results

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