Treebeard, Gracious Host, Agatha's Soul Cauldron, and Spike Feeder

Prerequisites

• Treebeard, Gracious Host on the battlefield
• Agatha's Soul Cauldron on the battlefield
• Spike Feeder in exile
• Treebeard has at least one +1/+1 counter on it

Steps

1. Activate Treebeard using Spike Feeder's second ability by removing a +1/+1 counter from it, causing you to gain 2 life
2. Treebeard triggers, putting two +1/+1 counters on itself
3. Repeat

Results

• Infinite +1/+1 counters on Treebeard and Halflings and Treefolk you control
• Infinite lifegain
• Infinite lifegain triggers