Mikaeus, the Unhallowed, Crystalline Crawler, and Phyrexian Altar

Prerequisites

• Mikaeus, the Unhallowed on the battlefield
• Crystalline Crawler on the battlefield
• Phyrexian Altar on the battlefield

Steps

1. If Crystalline Crawler has a +1/+1 counter on it, activate its first ability by removing a +1/+1 counter from it, adding one mana of any color
2. Repeat step 1 until Crystalline Crawler has no +1/+1 counters on it
3. Activate Phyrexian Altar by sacrificing Crystalline Crawler, adding one mana of any color
4. Crystalline Crawler dies, triggering its undying ability, returning it to the battlefield with a +1/+1 counter on it
5. Repeat

Results

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