Eirdu, Carrier of Dawn // Isilu, Carrier of Twilight, Bloodthrone Vampire, and Gleeful Arsonist

Prerequisites

• Eirdu, Carrier of Dawn // Isilu, Carrier of Twilight on the battlefield
• Bloodthrone Vampire on the battlefield
• Gleeful Arsonist on the battlefield

Steps

1. Activate Bloodthrone Vampire by sacrificing Gleeful Arsonist When Gleeful Arsonist dies, its undying ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it
2. Activate Bloodthrone Vampire by sacrificing Gleeful Arsonist When Gleeful Arsonist dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it
3. Resolve both Bloodthrone Vampire abilities from step 1 and 3
4. Repeat

Results

• Infinite creature ETB
• Infinite creature LTB
• Infinite creature sacrifice triggers
• Infinite death triggers
• Infinitely large creature until end of turn