Phyrexian Altar + Retribution of the Ancients

B identity

Commander legal

The 2 combo pieces

• Phyrexian Altar
• Retribution of the Ancients

How to execute it

1. Activate Phyrexian Altar by sacrificing the undying creature, adding {B}.
2. When the undying creature dies, its undying ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it.
3. Activate Retribution of the Ancients by paying {B} and removing a +1/+1 counter from the undying creature, giving any creature -1/-1 until end of turn.
4. Repeat.

What the combo produces

• Infinite creature LTB
• Infinite death triggers
• Infinite ETB
• Infinite sacrifice triggers
• Reduce the toughness of creatures opponents control to 0