Grenzo, Dungeon Warden + The Cauldron of Eternity + Phyrexian Altar + Dark Ritual + Timeless Witness

Grenzo, Dungeon Warden

The Cauldron of Eternity

Phyrexian Altar

Dark Ritual

Timeless Witness

How it works

1. Cast Dark Ritual by paying , adding .
2. Activate Phyrexian Altar by sacrificing Timeless Witness, adding one mana of any color.
3. When Timeless Witness dies, The Cauldron of Eternity triggers, putting Timeless Witness from your graveyard onto the bottom of your library.
4. Activate Grenzo by paying 2, putting Timeless Witness from the bottom of your library into your graveyard, and then putting it onto the battlefield.
5. When Timeless Witness enters the battlefield, it triggers, returning Dark Ritual from your graveyard to your hand.
6. Repeat.
7. Once you have infinite mana, you may activate Grenzo's ability any number of times.

This elegant loop relies on Grenzo, Dungeon Warden to constantly dredge creatures from the bottom of your library, a position maintained by The Cauldron of Eternity's replacement effect whenever a creature dies. By sacrificing Timeless Witness to Phyrexian Altar, you generate the mana needed to fund Grenzo's ability while feeding the very death trigger that sends the Witness back to the library's depths. Each time Timeless Witness returns to the battlefield, its enters-the-battlefield ability claws Dark Ritual back from your graveyard to your hand, allowing you to continually net positive mana and execute the loop indefinitely.