Requires

Double Major must be in hand. Twincast must be in hand. Dualcaster Mage must be in hand. Mana needed:

Steps

1. Cast Dualcaster Mage for .
2. Holding priority, cast Double Major targeting Dualcaster Mage.
3. Holding priority, cast Twincast, copying Double Major, targeting Dualcaster.
4. Let the copied Double Major resolve, creating a token copy of Dualcaster Mage.
5. Dualcaster Mage enters the battlefield, copying Double Major, targeting Dualcaster Mage.
6. Repeat from Step 4.

Results