The Jolly Balloon Man, Agatha's Soul Cauldron, Midnight Guard, and Mana Echoes

Prerequisites

• The Jolly Balloon Man in exile
• Agatha's Soul Cauldron on the battlefield
• Midnight Guard on the battlefield
• Mana Echoes on the battlefield
• Midnight Guard has at least one +1/+1 counter on it
• Midnight Guard does not have summoning sickness
• You control at least one additional nonlegendary creature
• available

Steps

1. Activate Midnight Guard using The Jolly Balloon Man's ability by paying and tapping it, creating a token copy of another nonlegendary creature you control that is a 1/1 Balloon with flying and haste in addition to its other types
2. When the creature token enters the battlefield, Midnight Guard and Mana Echoes trigger
3. Resolve the Midnight Guard trigger, untapping it
4. Resolve the Mana Echoes trigger, adding for each creature you control that shares a creature type with the creature token
5. Repeat

Results

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