Mairsil, the Pretender, Blood Vassal, Endling, and Workhorse

Prerequisites

• Mairsil, the Pretender on the battlefield
• Blood Vassal in exile
• Endling in exile
• Workhorse in exile
• Mairsil does not have a +1/+1 counter on it
• available

Steps

1. Activate Mairsil using Endling's third ability by paying , giving Mairsil undying until end of turn
2. Activate Mairsil using Blood Vassal's ability by sacrificing it, adding
3. Mairsil dies, triggering its undying ability, returning it from your graveyard to the battlefield with a +1/+1 counter on it
4. Activate Mairsil using Workhorse's ability by removing a +1/+1 counter from it, adding
5. Repeat

Results

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