Mikaeus, the Unhallowed + Moonshadow + Phyrexian Altar

B identity

Commander legal

The 3 combo pieces

• Mikaeus, the Unhallowed
• Moonshadow
• Phyrexian Altar

How to execute it

1. Activate Phyrexian Altar by sacrificing Moonshadow.
2. When Moonshadow 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.

What the combo produces

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