Dualcaster Mage, Phantom Train, and Behold the Sinister Six!

Prerequisites

• Dualcaster Mage in hand
• Phantom Train on the battlefield
• Behold the Sinister Six! in hand
• 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 Phantom Train 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 creature sacrifice triggers
• Infinite death triggers
• Infinite magecraft triggers
• Infinite recursion of creature cards in your graveyard
• Infinite +1/+1 counters on a creature
• Infinite creature LTB
• Infinite creature ETB