Lost Jitte + Karn's Bastion + Cryptic Trilobite + Solid Ground

Lost Jitte

Karn's Bastion

Cryptic Trilobite

Solid Ground

How it works

1. Activate Karn's Bastion by paying 4, putting a charge counter 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.