Dualcaster Mage, Fearsome Awakening, and Grimgrin, Corpse-Born

Prerequisites

• Dualcaster Mage in hand
• Fearsome Awakening in hand
• Grimgrin, Corpse-Born on the battlefield
• available

Steps

1. Cast Fearsome Awakening by paying its mana cost
2. Holding priority, cast Dualcaster Mage by paying its mana cost
3. When Dualcaster Mage enters, it triggers, targeting Fearsome Awakening
4. Holding priority, activate Grimgrin by sacrificing Dualcaster Mage, putting a +1/+1 counter on Grimgrin and untapping it
5. Resolve the Dualcaster Mage trigger, copying Fearsome Awakening Resolve the Fearsome Awakening copy, returning Dualcaster Mage from your graveyard to the battlefield
6. Repeat from step 3

Results

• Infinite +1/+1 counters on a creature
• Infinite creature ETB
• Infinite creature LTB
• Infinite creature sacrifice triggers
• Infinite death triggers
• Infinite magecraft triggers