Basalt Monolith + Tough Cookie + Agatha of the Vile Cauldron

Basalt Monolith

Tough Cookie

Agatha of the Vile Cauldron

How it works

1. Activate Tough Cookie's first ability by paying at most 1, causing Basalt Monolith to become a 4/4 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.