Mikaeus, the Unhallowed, Night of Souls' Betrayal, and Workhorse

Prerequisites

• Mikaeus, the Unhallowed on the battlefield
• Night of Souls' Betrayal on the battlefield
• Workhorse on the battlefield

Steps

1. Activate Workhorse by removing a +1/+1 counter from it, adding
2. Repeat step 1 until Workhorse does not have any +1/+1 counters on it
3. Workhorse dies as a state-based action due to having zero toughness
4. Workhorse's undying ability triggers, returning it from your graveyard to the battlefield with five +1/+1 counters on it
5. Repeat

Results

• Infinite colorless mana
• Infinite death triggers
• Infinite ETB
• Infinite LTB