Mikaeus, the Unhallowed, Pith Driller, and Phyrexian Altar

Prerequisites

• Mikaeus, the Unhallowed on the battlefield
• Pith Driller on the battlefield
• Phyrexian Altar on the battlefield
• Pith Driller does not have a +1/+1 counter on it

Steps

1. Activate Phyrexian Altar by sacrifiicing Pith Driller, adding one mana of any color
2. When Pith Driller dies, its undying ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it
3. When Pith Driller enters the battlefield, it triggers, putting a -1/-1 counter on it
4. Repeat

Results

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