Myr Battlesphere + Mimic Vat + Clock of Omens + Grim Monolith

Myr Battlesphere

Mimic Vat

Clock of Omens

Grim Monolith

How it works

1. Activate Grim Monolith's first ability by tapping it, adding CCC.
2. Activate Mimic Vat by paying 3 and tapping it, creating a token copy of Myr Battlesphere with haste.
3. Myr Battlesphere enters the battlefield, creating four 1/1 Myr creature tokens.
4. Activate Clock of Omens by tapping two Myrs, untapping Mimic Vat.
5. Activate Clock of Omens by tapping two Myrs, untapping Grim Monolith.
6. Repeat.