Shalai and Hallar, and Archangel of Thune

Prerequisites

• Shalai and Hallar on the battlefield
• Archangel of Thune on the battlefield
• You have a way to give Shalai and Hallar lifelink
• You have a way to put a +1/+1 counter on a creature you control

Steps

1. Put a +1/+1 counter on a creature you control
2. Shalai and Hallar triggers, dealing 1 damage to an opponent and causing you to gain one life
3. Archangel of Thune triggers, putting a +1/+1 counter on each creature you control
4. Shalai and Hallar triggers for each creature who had a counter placed on it this way
5. Resolve the first trigger, dealing 1 damage to an opponent and causing you to gain one life
6. Repeat from step 3

Results

• Infinite +1/+1 counters
• Infinite damage
• Infinite lifegain
• Infinite lifegain triggers