Necrotic Ooze, Barrenton Medic, and Morselhoarder

Prerequisites

• Necrotic Ooze on the battlefield
• Barrenton Medic in the graveyard
• Morselhoarder in the graveyard
• Necrotic Ooze does not have summoning sickness

Steps

1. Activate Necrotic Ooze using Barrenton Medic's second ability by putting a -1/-1 counter on it, untapping it
2. Activate Necrotic Ooze using Morselhoarder's ability by removing a -1/-1 counter from it, adding one mana of any color
3. Repeat

Results

• Infinite colored mana