Shelob, Child of Ungoliant, Devoted Druid, and Viridian Longbow

Prerequisites

• Shelob, Child of Ungoliant on the battlefield
• Devoted Druid on the battlefield
• Viridian Longbow on the battlefield
• Viridian Longbow attached to Shelob
• Shelob does not have summoning sickness

Steps

1. Activate Shelob by tapping it, dealing 1 damage to Devoted Druid
2. Devoted Druid dies as a state-based action due to Shelob's deathtouch
3. Shelob triggers, creating a token copy of Devoted Druid that is a Food artifact
4. Activate the Devoted Druid token by tapping it, adding
5. Activate the Devoted Druid token by putting a -1/-1 counter on it, untapping it
6. Repeat from step 4

Results

• Infinite green mana