Primal Prayers + Enduring Renewal + Phyrexian Altar

Primal Prayers

Enduring Renewal

Phyrexian Altar

How it works

1. Cast the creature that causes you to get energy counter(s) when it enters the battlefield by paying E due to Primal Prayers.
2. When the creature enters the battlefield, it triggers, causing you to get at least E.
3. Activate Phyrexian Altar by sacrificing the creature, adding one mana of any color.
4. When the creature dies, Enduring Renewal triggers, returning the creature from your graveyard to your hand.
5. Repeat.

This loop is a masterclass in resource conversion, using Primal Prayers to bypass normal mana restrictions by letting you cast small creatures entirely on energy. Once that creature hits the battlefield, Phyrexian Altar is right there to cleanly sacrifice it for any color of mana while fueling your death and sacrifice triggers. The true engine holding it all together is Enduring Renewal, whose passive trigger catches that dying creature on its way to the graveyard and effortlessly loops it right back to your hand. Because Enduring Renewal also forces you to reveal your hand and turns normal card draws of creatures into graveyard drops, it keeps your focus laser-locked on this infinite loop of casting, sacrificing, and recurring.