Carnifex Demon + Mikaeus, the Unhallowed + Phyrexian Altar

B identity

Commander legal

The 3 combo pieces

• Carnifex Demon
• Mikaeus, the Unhallowed
• Phyrexian Altar

How to execute it

1. Activate Phyrexian Altar by sacrificing Carnifex Demon.
2. When Carnifex Demon 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