Dualcaster Mage, Behold the Sinister Six!, and Yahenni, Undying Partisan

Prerequisites

• Dualcaster Mage in hand
• Behold the Sinister Six! in hand
• Yahenni, Undying Partisan on the battlefield
• available

Steps

1. Cast Behold the Sinister Six! by paying its mana cost Holding priority, cast Dualcaster Mage by paying its mana cost
2. When Dualcaster Mage enters, it triggers, targeting Behold the Sinister Six!
3. Holding priority, activate Yahenni by sacrificing Dualcaster Mage
4. Resolve the Dualcaster Mage trigger, copying Behold the Sinister Six!, with the copy targeting Dualcaster Mage Resolve the Behold the Sinister Six! 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 recursion of creature cards in your graveyard