Yannik, Scavenging Sentinel, Changeling Titan, and Lagrella, the Magpie

Prerequisites

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

Steps

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

Results

• Infinite +1/+1 counters on creatures you control
• Infinite creature ETB
• Infinite creature LTB