Mortuary + Goblin Bombardment + Phyrexian Walker + Bolas's Citadel

Mortuary

Goblin Bombardment

Phyrexian Walker

Bolas's Citadel

How it works

1. Activate Goblin Bombardment by sacrificing Phyrexian Walker
2. When Phyrexian Walker dies, Mortuary triggers, putting Phyrexian Walker from your graveyard onto the top of your library.
3. Resolve the Goblin Bombardment ability.
4. Cast Phyrexian Walker from the top of your library by paying 0 life.
5. Repeat.

This clever loop turns the zero-cost artifact creature Phyrexian Walker into an endless supply of ammunition. With Bolas's Citadel allowing you to play the top card of your library at the cost of life rather than mana, and Mortuary intercepting any creature that hits your graveyard to slide it right back to that very same top spot, the Walker simply cycles endlessly between battlefield and library. Goblin Bombardment provides the sacrificial outlet to fire off infinite damage at any target, easily fueled by Phyrexian Walker's zero mana value which ensures you pay zero life to recast it over and over.