Ashnod's Altar + Kithkin Spellduster + Thran Vigil

Ashnod's Altar

Kithkin Spellduster

Thran Vigil

How it works

1. Activate Ashnod's Altar by sacrificing Kithkin Spellduster.
2. When Kithkin Spellduster dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it.
3. Thran Vigil triggers, putting a +1/+1 counter on Kithkin Spellduster.
4. Repeat.

This loop turns Ashnod's Altar into a generator of infinite colorless mana and death triggers by continuously recycling Kithkin Spellduster through the graveyard. The magic that keeps this engine from burning out is Thran Vigil, whose passive ability triggers whenever a creature leaves your graveyard during your turn, placing a +1/+1 counter on Kithkin Spellduster. Because state-based actions cause +1/+1 and -1/+1 counters to annihilate each other, Kithkin Spellduster enters the battlefield clean of its previous penalty and ready to be sacrificed to Ashnod's Altar all over again.