Changeling Titan, Lagrella, the Magpie, and Hostage Taker

Prerequisites

• Changeling Titan in hand or on the battlefield or in exile
• Lagrella, the Magpie in hand or on the battlefield or in exile
• Hostage Taker in hand or on the battlefield or in exile
• plus the mana cost of the creature in your hand available

Steps

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

Results

• Infinite creature ETB
• Infinite creature LTB