Mikaeus, the Unhallowed, Grim Poppet, and Phyrexian Altar

Prerequisites

• Mikaeus, the Unhallowed on the battlefield
• Grim Poppet on the battlefield
• Phyrexian Altar on the battlefield

Steps

1. Activate Phyrexian Altar by sacrificing Grim Poppet, adding one mana of any color
2. Grim Poppet dies, triggering its undying ability, returning it from your graveyard to the battlefield with two -1/-1 counters on it
3. Repeat

Results

• Infinite -1/-1 counters
• Infinite colored mana
• Infinite death triggers
• Infinite ETB
• Infinite LTB
• Infinite sacrifice triggers