Shalai and Hallar, and Phyrexian Devourer

Prerequisites

• Shalai and Hallar on the battlefield
• Phyrexian Devourer on the battlefield

Steps

1. Activate Phyrexian Devourer by exiling the top card of your library, putting a number of +1/+1 counters on it equal to the card's mana value
2. Shalai and Hallar triggers if counters were placed this way, as well as Phyrexian Devourer if its power is seven or greater
3. Resolve the Shalai and Hallar trigger, dealling one damage to an opponent for each counter placed this way
4. Holding priority, repeat from step 1

Results

• Exile your library
• Near-infinite damage