Basalt Monolith + Agatha of the Vile Cauldron + Karn, the Great Creator

Basalt Monolith

Agatha of the Vile Cauldron

Karn, the Great Creator

How it works

1. Activate Karn's first loyalty ability by putting a loyalty counter on it, causing Basalt Monolith to become a 3/3 artifact creature until end of turn.
2. Activate Basalt Monolith's first ability by tapping it, adding CCC.
3. activate Basalt Monolith's second ability by paying at most 2, untapping it.
4. Repeat from step 2.