Myr Propagator + Umbral Mantle + Krark-Clan Ironworks + Power Artifact

Myr Propagator

Umbral Mantle

Krark-Clan Ironworks

Power Artifact

How it works

1. Activate Myr Propagator by paying 1 and tapping it, creating a token copy of itself.
2. Activate Krark-Clan Ironworks by sacrificing the Myr Propagator token, adding CC.
3. Activate Myr Propagator by paying 1 and untapping it, giving itself +2/+2 until end of turn.
4. Repeat.

This intricate loop relies on heavy mana-reduction and untapping to flood the board with mechanical replicas. By reducing the activation costs with Power Artifact, Umbral Mantle allows the original Myr Propagator to untap for just {1}, which conveniently matches the discounted cost to activate its token-copy ability. Once you have a spare copy lying around, Krark-Clan Ironworks steps in to convert it into raw colorless mana, fueling the engine to repeat the process infinitely and swell your board presence beyond measure.