Metalwork Colossus + The Ooze + Woe Strider + Master Biomancer

Metalwork Colossus

The Ooze

Woe Strider

Master Biomancer

How it works

1. Cast Metalwork Colossus by paying 0, which enters with at least two +1/+1 counters on it due to Master Biomancer.
2. Activate Woe Strider by sacrificing Metalwork Colossus.
3. When Metalwork Colossus dies, The Ooze triggers, creating a Mutagen token for each +1/+1 counter Metalwork Colossus had.
4. Resolve the Woe Strider ability.
5. Activate Metalwork Colossus by sacrificing two Mutagens, returning it from your graveyard to your hand.
6. Repeat.

This ingenious loop turns the massive mana-value discount of Metalwork Colossus into a self-sustaining engine by letting you cast it for free. Master Biomancer ensures that the Colossus enters the battlefield with a fresh batch of +1/+1 counters, setting up The Ooze to harvest those counters and flood your board with Mutagen tokens whenever the Colossus leaves. From there, Woe Strider provides a reliable sacrifice outlet to send the Colossus back to the graveyard, where its own ability uses those very same Mutagen tokens as the two sacrificed artifacts to return it straight to your hand.