Mortuary + Grim Haruspex + Stonecoil Serpent

Mortuary

Grim Haruspex

Stonecoil Serpent

How it works

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

This clever loop relies on Stonecoil Serpent's unique ability to be cast for zero mana, causing it to instantly hit the graveyard as a state-based action upon entering the battlefield. Mortuary catches the creature right as it dies, instantly shuffling it back to the top of your library instead of letting it rest in the graveyard. Meanwhile, Grim Haruspex watches the chaos unfold, turning every single one of those tragic demises into a fresh card draw that puts Stonecoil Serpent right back into your hand, ready to be cast for free all over again.