Dualcaster Mage, and Justiciar's Portal

Prerequisites

• Dualcaster Mage in hand
• Justiciar's Portal in hand
• available

Steps

1. Cast Justiciar's Portal by paying its mana cost
2. Holding priority, cast Dualcaster Mage by paying its mana cost
3. When Dualcaster Mage enters, it triggers, copying Justiciar's Portal, with the copy targeting Dualcaster Mage
4. Resolve the copy of Justiciar's Portal, blinking Dualcaster Mage
5. Repeat from step 3

Results

• Infinite ETB
• Infinite LTB
• Infinite magecraft triggers