Mikaeus, the Unhallowed, Phyrexian Altar, and Grim Poppet

Prerequisites

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

Steps

1. Activate Phyrexian Altar by sacrificing Grim Poppet
2. When Grim Poppet dies, its undying ability triggers, returning it from your graveyard to the battlefield without a +1/+1 counter on it due to its replacement effect
3. Repeat

Results

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