Mikaeus, the Unhallowed, Phyrexian Altar, and The Reaper, King No More

Prerequisites

• Mikaeus, the Unhallowed on the battlefield
• Phyrexian Altar on the battlefield
• The Reaper, King No More on the battlefield

Steps

1. Activate Phyrexian Altar by sacrificing The Reaper
2. When The Reaper dies, its undying ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it
3. When The Reaper enters the battlefield, it triggers, putting a -1/-1 counter on it
4. Repeat

Results

• Infinite ETB
• Infinite LTB
• Infinite colored mana
• Infinite death triggers
• Infinite sacrifice triggers
• Infinite -1/-1 counters
• Infinite recursion of non-Human creatures you control