Mortuary, Bolas's Citadel, Blood Pet, and Arnyn, Deathbloom Botanist

Prerequisites

• Mortuary on the battlefield
• Bolas's Citadel on the battlefield
• Blood Pet in hand
• Arnyn, Deathbloom Botanist on the battlefield

Steps

1. Cast Blood Pet by paying its mana cost
2. Activate Blood Pet by sacrificing it
3. When Blood Pet dies, Mortuary and Arnyn trigger
4. Resolve the Mortuary trigger, putting Blood Pet from your graveyard onto the top of your library
5. Resolve the Arnyn trigger, causing target opponent to lose 2 life and you to gain 2 life
6. Cast Blood Pet from the top of your library by paying 1 life
7. Repeat from step 2

Results

• Infinite creature ETB
• Infinite creature LTB
• Infinite black mana
• Infinite death triggers
• Infinite lifegain triggers
• Infinite lifeloss
• Infinite creature sacrifice triggers
• Infinite storm count