Mairsil, the Pretender, Endling, Cauldron of Souls, Blood Pet, and Anger

Prerequisites

• Mairsil, the Pretender on the battlefield
• Endling in exile
• Cauldron of Souls in exile
• Blood Pet in exile
• Anger in the graveyard
• You control a Mountain

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 Endling's third ability by paying , giving Mairsil undying until end of turn
5. Activate Mairsil using Blood Pet's ability by sacrificing it, adding
6. When Mairsil dies, its undying ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it
7. Repeat

Results

• Infinite black mana
• Infinite death triggers
• Infinite ETB
• Infinite LTB
• Infinite sacrifice triggers