Beledros Witherbloom + Urza's Saga + Agatha's Soul Cauldron + Arwen, Weaver of Hope + Gristleback

Beledros Witherbloom

Urza's Saga

Agatha's Soul Cauldron

Arwen, Weaver of Hope

Gristleback

How it works

1. Activate any number of lands except Urza's Saga by tapping them, adding at least 2.
2. Activate Urza's Saga's second ability by paying 2 and tapping it, creating a 0/0 Construct artifact creature token that gets +1/+1 for each artifact you control, and that enters the battlefield with a number of +1/+1 counters equal to Arwen's toughness.
3. Activate the Construct using Beledros Witherbloom's ability by paying 10 life, untapping all lands you control.
4. Activate the Construct using Gristleback's ability by sacrificing it, causing you to gain at least 10 life.
5. Repeat.
6. If the number of artifacts you control plus Arwen's toughness is equal to or greater than 10, this combo nets infinite life, and if other lands you control can tap to produce at least 3, this combo nets infinite mana.
7. If you get infinite life and infinite mana, you may forego sacrificing the Constructs.

This intricate loop transforms life into mana and back again by harmonizing graveyard hate with land-untapping power. The engine relies on Agatha's Soul Cauldron to feed activated creature abilities to your board, drawing from a Gristleback previously exiled into the Cauldron to gain life from sacrifice, and Beledros Witherbloom to untap your lands at the cost of 10 life. Meanwhile, Urza's Saga churns out Construct tokens that naturally enter the battlefield beefed up with +1/+1 counters courtesy of Arwen, Weaver of Hope, giving those fresh tokens the exact toughness and stat line needed to successfully fuel the Cauldron's gifted abilities. As long as you can manage the initial life payments and math, the loop sustains itself indefinitely.