Agatha's Soul Cauldron, Immaculate Magistrate, and Devoted Druid

Prerequisites

• Agatha's Soul Cauldron on the battlefield
• Immaculate Magistrate on the battlefield
• Devoted Druid in exile
• You control at least two Elves
• Immaculate Magistrate does not have summoning sickness

Steps

1. Activate Immaculate Magistrate by tapping it, putting a +1/+1 counter on it for each Elf you control
2. Activate Immaculate Magistrate using Devoted Druid's second ability by putting a -1/-1 counter on it, untapping it
3. Repeat
4. Once you have infinite +1/+1 counters on Immaculate Magistrate, you may instead target any other creature, or use Devoted Druid's first ability
5. If you give other creatures +1/+1 counters, you may also untap them infinitely using Devoted Druid's second ability

Results

• Infinite +1/+1 counters
• Infinite green mana
• Infinite mana creatures you control can produce
• Infinite untap of creatures you control