Walking Ballista, Unspeakable Symbol, Angrath's Marauders, and Twinflame Tyrant

Prerequisites

• Walking Ballista on the battlefield
• Unspeakable Symbol on the battlefield
• Angrath's Marauders on the battlefield
• Twinflame Tyrant on the battlefield
• You have a way to give Walking Ballista lifelink
• Walking Ballista has at least two +1/+1 counters on it, or your life total is at least 4

Steps

1. Give Walking Ballista lifelink, if needed
2. If Walking Ballista has less than two +1/+1 counters on it, activate Unspeakable Symbol by paying 3 life, putting a +1/+1 counter on Walking Ballista
3. Activate Walking Ballista's second ability by removing a +1/+1 counter from it, dealing 4 damage to an opponent or a permanent an opponent controls, and causing you to gain 4 life
4. Repeat from step 2

Results

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