Rex, Cyber-Hound, Pili-Pala, and Harabaz Druid

Prerequisites

• Rex, Cyber-Hound on the battlefield
• Pili-Pala in exile
• Harabaz Druid in exile
• You control at least two Allies
• Rex does not have summoning sickness
• Harabaz Druid and Pili-Pala exiled with a brain counter on them

Steps

1. Activate Rex using Harabaz Druid's ability by tapping it, adding two mana of any color
2. Activate Rex using Pili-Pala's ability by paying and untapping it, adding one mana of any color
3. Repeat

Results

• Infinite colored mana