Umbral Collar Zealot, Dualcaster Mage, and Leonardo's Technique

Prerequisites

• Umbral Collar Zealot on the battlefield
• Dualcaster Mage in hand
• Leonardo's Technique in hand
• available

Steps

1. Cast Leonardo's Technique by paying its mana cost, targeting any applicable target
2. Holding priority, cast Dualcaster Mage by paying its mana cost
3. When Dualcaster Mage enters, it triggers, targeting Leonardo's Technique
4. Holding priority, activate Umbral Collar Zealot by sacrificing Dualcaster Mage
5. Resolve the Dualcaster Mage trigger, copying Leonardo's Technique, with the copy targeting Dualcaster Mage Resolve the Leonardo's Technique copy, returning Dualcaster Mage from your graveyard to the battlefield
6. Repeat from step 3

Results

• Infinite ETB
• Infinite LTB
• Infinite death triggers
• Infinite magecraft triggers
• Infinite recursion of creature cards in your graveyard
• Infinite sacrifice triggers
• Infinite surveil