Greenweaver Druid, Umbral Mantle, and Biomancer's Familiar

Prerequisites

• Greenweaver Druid on the battlefield
• Umbral Mantle on the battlefield
• Biomancer's Familiar on the battlefield
• Umbral Mantle attached to Greenweaver Druid
• Greenweaver Druid does not have summoning sickness

Steps

1. Activate Greenweaver Druid by tapping it, adding
2. Activate Greenweaver Druid by paying and untapping it, giving itself +2/+2 until end of turn
3. Repeat

Results

• Infinitely large Greenweaver Druid until end of turn
• Infinite green mana