Krark-Clan Ironworks + Lesser Masticore + Serra Redeemer

Krark-Clan Ironworks

Lesser Masticore

Serra Redeemer

How it works

1. Activate Krark-Clan Ironworks by sacrificing Lesser Masticore
2. When Lesser Masticore dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it.
3. When Lesser Masticore enters, Serra Redeemer triggers, putting a +1/+1 counter on Lesser Masticore
4. Repeat.

This loop turns the recycling engine of Lesser Masticore into a fountain of colorless mana by leaning on Krark-Clan Ironworks to continuously sacrifice the creature for {C}{C}. Because Lesser Masticore enters the graveyard and triggers persist, it comes back with a -1/-1 counter, but Serra Redeemer instantly swoops in to neutralize that drawback by placing two +1/+1 counters on it upon entry, which conveniently annihilates both counters via state-based actions. This leaves the mechanical mouse fresh and ready to be fed back into Krark-Clan Ironworks, generating an endless cascade of sacrifice triggers and pure mana.