Necrotic Ooze, Llanowar Vanguard, and Devoted Druid

Prerequisites

• Necrotic Ooze on the battlefield
• Llanowar Vanguard in the graveyard
• Devoted Druid in the graveyard

Steps

1. Activate Necrotic Ooze using Llanowar Vanguard's ability by tapping it, giving it +0/+4 until end of turn
2. Activate Necrotic Ooze using Devoted Druid's second ability by putting a -1/-1 counter on it, untapping it
3. Repeat
4. Once Necrotic Ooze has infinite toughness, you may instead use Devoted Druid's first ability to get infinite green mana

Results

• Infinite green mana