Lost Jitte + Karn's Bastion + Cryptic Trilobite + Pir, Imaginative Rascal

Lost Jitte

Karn's Bastion

Cryptic Trilobite

Pir, Imaginative Rascal

How it works

1. Activate Karn's Bastion by paying 4, putting two charge counters on Lost Jitte and two +1/+1 counters on Cryptic Trilobite.
2. Activate Cryptic Trilobite's first ability twice by removing two +1/+1 counters from it, adding CCCC that can only be spent to activate abilities.
3. Activate Lost Jitte by removing a charge counter from it, untapping Karn's Bastion.
4. Repeat.

This engine uses Pir, Imaginative Rascal's replacement effect to supercharge Karn's Bastion, allowing a single activation of its proliferate ability to add extra counters instead of just one. Cryptic Trilobite fuels this loop by converting its own growing size into the colorless mana required to repeatedly activate the Bastion, leveraging its restriction to pay for activated abilities. Meanwhile, Lost Jitte steps in as a versatile utility piece that can be charged up infinitely by the loop, allowing you to untap Karn's Bastion and keep the cascade of counters rolling indefinitely.