Yedora, Grave Gardener + Phyrexian Altar + Watcher of the Roost

Yedora, Grave Gardener

Phyrexian Altar

Watcher of the Roost

How it works

1. Activate Phyrexian Altar by sacrificing Watcher of the Roost, adding one mana of any color.
2. When Watcher of the Roost dies, Yedora triggers, returning Watcher of the Roost from your graveyard to the battlefield face down as a Forest land.
3. Activate Watcher of the Roost's morph ability by revealing a white card from your hand, turning it face up.
4. Watcher of the Roost triggers, causing you to gain 2 life.
5. Repeat.

This ingenious loop turns the circle of life into an infinite mana engine by exploiting the unique rules governing face-down permanents and alternative costs. When you sacrifice Watcher of the Roost to Phyrexian Altar, Yedora, Grave Gardener immediately catches it as it dies, resurrecting it face down as a Forest land. Because morph is a special action that doesn't use the stack and can be performed on any permanent (not just a creature), you can use Watcher of the Roost's morph ability to turn it right back face up by revealing a white card from your hand, resetting its state so it can be fed back into Phyrexian Altar once more. Along the way, every iteration of turning Watcher of the Roost face up triggers its own lifegain ability, netting you an endless stream of life, mana, and death triggers.