Rooftop Storm + Enduring Renewal + Rot-Tide Gargantua

Rooftop Storm

Enduring Renewal

Rot-Tide Gargantua

How it works

1. Cast Rot-Tide Gargantua by paying 0.
2. When Rot-Tide Gargantua enters the battlefield, it triggers, causing you to sacrifice it.
3. When Rot-Tide Gargantua dies, Enduring Renewal triggers, returning it to your hand from your graveyard.
4. Repeat.

This elegant loop relies on Rooftop Storm to cast our zombie for free, turning the mana cost of Rot-Tide Gargantua into a trivial {0}. Once it enters the battlefield, the gargantua's own exploit ability lets you sacrifice it immediately, triggering its sacrifice condition. That trip to the graveyard then wakes up Enduring Renewal, whose passive trigger catches the dying zombie and bounces it right back to your hand so you can cast it all over again.