Changeling Berserker, Changeling Titan, and Phantom Steed

Prerequisites

• Changeling Berserker in hand or on the battlefield or in exile
• Changeling Titan in hand or on the battlefield or in exile
• Phantom Steed in hand or on the battlefield or in exile
• plus the mana cost of the creature in your hand available

Steps

1. Cast Changeling Berserker for its mana cost
2. When Changeling Berserker enters, it exiles Changeling Titan until Changeling Berserker leaves the battlefield
3. Resolve any additional effects of Changeling Berserker's ETB
4. When Changeling Titan leaves the battlefield, Phantom Steed is returned from exile to the battlefield
5. When Phantom Steed enters, it exiles Changeling Berserker until Phantom Steed leaves the battlefield
6. Resolve any additional effects of Phantom Steed's ETB
7. When Changeling Berserker leaves the battlefield, Changeling Titan is returned from exile to the battlefield
8. When Changeling Titan enters, it exiles Phantom Steed until Changeling Titan leaves the battlefield
9. Resolve any additional effects of Changeling Titan's ETB
10. When Phantom Steed leaves the battlefield, Changeling Berserker is returned from exile to the battlefield
11. Repeat from step 2

Results

• Infinite creature ETB
• Infinite creature LTB