Marvin, Murderous Mimic, Phyrexian Devourer, and Walking Ballista

Prerequisites

• Marvin, Murderous Mimic on the battlefield
• Phyrexian Devourer on the battlefield
• Walking Ballista on the battlefield

Steps

1. Activate Marvin using Phyrexian Devourer's ability by exiling the top card of your library, putting a number of +1/+1 counters on Marvin equal to the exiled card's mana value
2. Repeat step 1 as desired or until you have an empty library
3. Activate Marvin using Walking Ballista's second ability by removing a +1/+1 counter from Marvin, dealing 1 damage to any target
4. Repeat step 3 as desired

Results

• Near-infinite damage
• Exile your library
• Near-infinite +1/+1 counters on Marvin