Necrotic Ooze, Devoted Druid, and Morselhoarder

Prerequisites

• Necrotic Ooze on the battlefield
• Devoted Druid in the graveyard
• Morselhoarder in the graveyard

Steps

1. Place a -1/-1 counter on Necrotic Ooze with Devoted Druid's ability and remove it with Morselhoarder's ability to add one mana of any color
2. Repeat

Results

• Infinite colored mana