Mairsil, the Pretender, Endling, Blood Pet, and Crystalline Crawler

Prerequisites

• Mairsil, the Pretender on the battlefield
• Endling in exile
• Blood Pet in exile
• Crystalline Crawler 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 Pet'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 Crystalline Crawler's first ability by removing a +1/+1 counter from it, adding one mana of any color
5. Repeat

Results

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