Toph, the First Metalbender, Haru, Hidden Talent, Xenograft, and Grimgrin, Corpse-Born

Prerequisites

• Toph, the First Metalbender on the battlefield
• Haru, Hidden Talent on the battlefield
• Xenograft on the battlefield
• Grimgrin, Corpse-Born on the battlefield

Steps

1. Cast any artifact creature by paying its mana cost
2. When the artifact creature enters as an Ally due to Xenograft, Haru triggers, earthbending the artifact creature, as it's a land due to Toph
3. Activate Grimgrin by sacrificing the artifact creature
4. When the creature dies, Haru triggers, returning the creature from your graveyard to the battlefield
5. When the creature enters as an Ally due to Xenograft, Haru triggers, earthbending the creature, as it's a land due to Toph
6. Resolve the Grimgrin ability, putting a +1/+1 counter on Grimgrin and untapping it
7. Repeat from step 3

Results

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