Agatha's Soul Cauldron, Bloodspore Thrinax, and Grist, the Hunger Tide

Prerequisites

• Agatha's Soul Cauldron on the battlefield
• Bloodspore Thrinax on the battlefield
• Grist, the Hunger Tide in exile
• Bloodspore Thrinax has at least one +1/+1 counter on it

Steps

1. Activate Bloodspore Thrinax using Grist's first loyalty ability by putting a loyalty counter on it, causing you to create a 1/1 Insect creature token and mill a card, and then put a loyalty counter on Bloodspore Thrinax and repeat the process if the card was an Insect
2. The Insect enters the battlefield with at least one +1/+1 counter on it due to Bloodspore Thrinax, causing it to have Grist's abilities
3. Repeat from step 1 using the Insect token instead

Results

• Infinite creature tokens
• Infinite ETB
• Infinite self-mill