Mortuary + Harvester of Souls + Walking Ballista

Mortuary

Harvester of Souls

Walking Ballista

How it works

1. Cast Walking Ballista by paying 0.
2. Walking Ballista enters and dies as a state-based action due to having 0 toughness, triggering Mortuary and Harvester of Souls.
3. Resolve the Mortuary trigger, putting Walking Ballista from your graveyard onto the top of your library.
4. Resolve the Harvester of Souls trigger, causing you to draw a card, thus drawing Walking Ballista from your library.
5. Repeat.

This ingenious loop turns the zero-mana casting of Walking Ballista into a perpetual motion machine, fueled entirely by its own tragic demise. The moment Walking Ballista hits the battlefield with zero toughness, Mortuary catches it on its way to the graveyard and neatly tucks it back onto the top of your library. Simultaneously, Harvester of Souls watches the nontoken creature perish and rewards you with a fresh card draw, placing Walking Ballista right back into your hand so you can cast it for zero once more.