Myr Propagator + Umbral Mantle + Krark-Clan Ironworks + Training Grounds

Myr Propagator

Umbral Mantle

Krark-Clan Ironworks

Training Grounds

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 brilliant loop transforms Training Grounds and Umbral Mantle into a profound discount and engine for your artifacts, dropping the untap cost of Umbral Mantle to just a single mana. With that reduction in place, you can tap Myr Propagator to clone itself using its ability, feed that fresh token to Krark-Clan Ironworks for a net profit of mana, and then use Umbral Mantle to untrap and pump the original Myr Propagator, leaving you with surplus colorless energy to repeat the cycle indefinitely.