Fathom Mage + Cleric Class + Sheoldred, the Apocalypse

Fathom Mage

Cleric Class

Sheoldred, the Apocalypse

How it works

1. Gain life.
2. Cleric Class triggers, putting a +1/+1 counter on Fathom Mage.
3. Fathom Mage triggers, causing you to draw a card.
4. Sheoldred triggers, causing you to gain 3 life.
5. Repeat from step 2.

This clever loop feeds entirely on itself once an initial source of life gets the ball rolling. With Cleric Class at Level 2, any life gain triggers a +1/+1 counter onto Fathom Mage, whose evolve-bolstered counters and natural abilities turn that into a card draw. That drawn card immediately rouses Sheoldred, the Apocalypse, whose replacement-boosted lifegain pushes back into Cleric Class to repeat the cycle indefinitely.