Activate Phyrexian Altar by sacrificing the creature, adding one mana of any color.
When the creature dies, Yedora triggers, returning the creature from your graveyard to the battlefield face-down as a Forest land.
Activate the creature by tapping it, adding .
Activate Primordial Mist by exiling the creature face-up, allowing you to play the creature from exile this turn.
Cast the creature from exile by paying its mana cost.
Repeat.
If the creature can be cast using one or less mana, this combo nets infinite mana.
This fascinating loop turns any creature that costs one or less mana into a self-sustaining engine by transforming the graveyard into a revolving door of land and spell. When you feed a creature to Phyrexian Altar, Yedora, Grave Gardener immediately rescues it from the graveyard, returning it to the battlefield as a face-down Forest land that can tap for green mana. To break it free from its leafy slumber, Primordial Mist lets you exile that face-down permanent to play it anew, allowing you to recast it cheaply and feed the Altar once more.