The Jolly Balloon Man, Agatha's Soul Cauldron, Midnight Guard, and Priest of Urabrask

Prerequisites

• The Jolly Balloon Man in exile
• Agatha's Soul Cauldron on the battlefield
• Midnight Guard on the battlefield
• Priest of Urabrask on the battlefield
• Midnight Guard has at least one +1/+1 counter on it
• Midnight Guard does not have summoning sickness
• available

Steps

1. Activate Midnight Guard using The Jolly Balloon Man's ability by paying and tapping it, creating a token copy of Priest of Urabrask that is a 1/1 Balloon with flying and haste in addition to its other types
2. When the Priest of Urabrask token enters the battlefield, it and Midnight Guard trigger
3. Resolve the Priest of Urabrask token's trigger, adding
4. Resolve the Midnight Guard trigger, untapping it
5. Repeat

Results

• Infinite LTB
• Infinite ETB
• Infinite sacrifice triggers
• Infinite death triggers
• Infinite creature tokens with haste
• Infinite token copies of each creature you control with haste except Midnight Guard
• Infinite red mana