Cathars' Crusade + Cauldron of Souls + Corridor Monitor + Phyrexian Altar

WU identity

Commander legal

The 4 combo pieces

What must be in place

Corridor Monitor does not have a -1/-1 counter on it.

How to execute it

  1. Activate Cauldron of Souls by tapping it, giving Corridor Monitor persist until end of turn.
  2. Activate Phyrexian Altar by sacrificing Corridor Monitor, adding one mana of any color.
  3. When Corridor Monitor dies, its persist ability triggers, returning itself from your graveyard to the battlefield with a -1/-1 counter on it.
  4. When Corridor Monitor enters the battlefield, it and Cathars' Crusade trigger.
  5. Resolve the Corridor Monitor trigger, untapping Cauldron of Souls.
  6. Resolve the Cathars' Crusade trigger, putting a +1/+1 counter on each creature you control.
  7. Repeat.

What the combo produces