Cloudstone Curio + Beastcaller Savant + Bosk Banneret + Crimson Kobolds

Cloudstone Curio

Beastcaller Savant

Bosk Banneret

Crimson Kobolds

How it works

1. Activate Beastcaller Savant by tapping it, adding that can only be spent to cast a creature spell.
2. Cast Crimson Kobolds by paying 0.
3. When Crimson Kobolds enters the battlefield, Cloudstone Curio triggers, returning Beastcaller Savant to your hand from the battlefield.
4. Cast Beastcaller Savant by paying due to Bosk Banneret.
5. When Beastcaller Savant enters the battlefield, Cloudstone Curio triggers, returning Crimson Kobolds to your hand from the battlefield.
6. Repeat.