Mortuary + Fecundity + Shifting Wall

Mortuary

Fecundity

Shifting Wall

How it works

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

This clever loop turns the self-sacrificing nature of Shifting Wall into a perpetual engine by casting it for zero mana. As soon as it enters the battlefield and promptly perishes from having zero toughness, both Mortuary and Fecundity spring into action to recycle it. Mortuary neatly places the creature back on top of your library while Fecundity rewards you for the death by letting you draw it right back into your hand, ready to cast all over again.