Mairsil, the Pretender, Carnifex Demon, Cauldron of Souls, Blood Pet, and Urabrask the Hidden

Prerequisites

• Mairsil, the Pretender on the battlefield
• Carnifex Demon in exile
• Cauldron of Souls in exile
• Blood Pet in exile
• Urabrask the Hidden on the battlefield
• Mairsil does not have a -1/-1 counter on it

Steps

1. Activate Mairsil using Cauldron of Souls' ability by tapping it, giving itself persist until end of turn
2. Activate Mairsil using Blood Pet's ability by sacrificing it, adding
3. When Mairsil dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it
4. Activate Mairsil using Carnifex Demon's ability by paying and removing a -1/-1 counter from it, putting a -1/-1 counter on each other creature
5. Repeat

Results

• Infinite death triggers
• Infinite ETB
• Infinite LTB
• Infinite sacrifice triggers