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

Prerequisites

• Rex, Cyber-Hound on the battlefield
• Pili-Pala in exile
• Incubation Druid in exile
• Rex does not have summoning sickness and has a +1/+1 counter on it
• You control a mana-producing land
• Incubation Druid and Pili-Pala exiled with a brain counter on them

Steps

1. Activate Rex using Incubation Druid's ability by tapping it, adding three mana of any type a land you control could produce
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
• Infinite mana lands you control can produce