Umbral Collar Zealot, Dualcaster Mage, and Black Sun's Twilight

Prerequisites

• Umbral Collar Zealot on the battlefield
• Dualcaster Mage in hand
• Black Sun's Twilight in hand
• available

Steps

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

Results

• Infinite LTB
• Infinite ETB
• Infinite sacrifice triggers
• Infinite death triggers
• Infinite magecraft triggers
• Infinite surveil 1