Necrotic Ooze + Llanowar Vanguard + Devoted Druid

Necrotic Ooze

Llanowar Vanguard

Devoted Druid

How it works

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.

This ingenious loop turns Necrotic Ooze into a one-stop mana engine by absorbing the gifts of fallen comrades. While Devoted Druid usually destroys itself with its own -1/-1 counters, Necrotic Ooze bypasses this limitation by layering in Llanowar Vanguard's activated ability; by constantly pumping up the Ooze's toughness in response to the self-inflicted damage, it safely absorbs an infinite number of untap triggers. Once your toughness buffer is securely in the stratosphere, you can finally tap the Ooze for mana using Devoted Druid's other ability without fear, washing away all your mana restrictions in a single bubbling surge of green energy.