Mikaeus, the Unhallowed + Phyrexian Altar + Workhorse

B identity

Commander legal

The 3 combo pieces

How to execute it

  1. Activate Workhorse by removing all +1/+1 counters, adding that many {C}.
  2. Activate Phyrexian Altar by sacrificing Workhorse, adding one mana of any color.
  3. Workhorse undying ability triggers, returning it to the battlefield with an additional +1/+1 counter on it.
  4. Repeat.

What the combo produces