Incubation Druid, Umbral Mantle, and Nyxbloom Ancient

Prerequisites

• Incubation Druid on the battlefield
• Umbral Mantle on the battlefield
• Nyxbloom Ancient on the battlefield
• Umbral Mantle attached to Incubation Druid
• Incubation Druid does not have summoning sickness
• Incubation Druid has at least one +1/+1 counter on it

Steps

1. Activate Incubation Druid's first ability by tapping it, adding nine mana of any color a land you control could produce
2. Activate Incubation Druid by paying and untapping it, giving itself +2/+2 until end of turn
3. Repeat

Results

• Infinitely large Incubation Druid until end of turn
• Infinite mana lands you control can produce