Voltaic Construct + Rise and Shine + Grim Monolith

Voltaic Construct

Rise and Shine

Grim Monolith

How it works

1. Animate Grim Monolith using Rise and Shine.
2. Activate Grim Monolith by tapping it, adding CCC.
3. Activate Voltaic Construct by paying 2, untapping Grim Monolith.
4. Repeat from step 2.

This engine breathes sudden life into cold metal by casting Rise and Shine for its overload cost, turning your Grim Monolith into a living artifact creature padded with four +1/+1 counters. Because Grim Monolith is now a creature, Voltaic Construct can target it with its ability to untap it for just two mana. Tap the Monolith for three colorless mana, use two of that mana to activate the Construct, and you are left profiting one mana each time you repeat the loop.