Mortuary + Stonecoil Serpent + Fecundity

Mortuary

Stonecoil Serpent

Fecundity

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 Fecundity.
3. Resolve the Mortuary trigger, putting Stonecoil Serpent from your graveyard onto the top of your library.
4. Resolve the Fecundity trigger, causing you to draw a card, thus drawing Stonecoil Serpent from your library.
5. Repeat.

This clever loop lets you endlessly recast a single artifact creature for free by turning the graveyard into your personal library deck. When you cast Stonecoil Serpent for zero mana, state-based actions immediately send it to the graveyard, which is where Mortuary steps in to instantly rescue it by placing it right back on top of your library. From there, Fecundity triggers upon its death to let you draw the very card you just tucked away, putting Stonecoil Serpent back in your hand and ready to replay. Because every iteration costs no mana and replaces itself instantly, this recursive engine generates infinite creature enters-the-battlefield events, death triggers, and draw triggers without ever running out of steam.