Marvin, Murderous Mimic + Phyrexian Devourer + Walking Ballista

Marvin, Murderous Mimic

Phyrexian Devourer

Walking Ballista

How it works

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.

This loop turns Marvin, Murderous Mimic into a lethal engine by stitching together the text of two mechanical powerhouses. Because Marvin inherits all activated abilities from creatures you control, it gains Phyrexian Devourer's ability to pump its own stats by exiling cards from your library, while simultaneously dodging the Devourer's built-in safety valve because Marvin's name is different. Once Marvin's power balloons to a massive size from the exiled mana values, it taps into Walking Ballista's ability to strip those accumulated +1/+1 counters away, converting them into a torrent of direct damage to any target until the battlefield is clear.