Ulasht, the Hate Seed + Agatha's Soul Cauldron + Wildwood Mentor + Phyrexian Altar

Ulasht, the Hate Seed

Agatha's Soul Cauldron

Wildwood Mentor

Phyrexian Altar

How it works

1. Activate Wildwood Mentor using Ulasht's ability by paying 1 and removing a +1/+1 counter from it, creating a 1/1 Saproling creature token.
2. When the Saproling enters the battlefield, Wildwood Mentor's first ability triggers, putting a +1/+1 counter on itself.
3. Activate Phyrexian Altar by sacrificing the Saproling, adding 1.
4. Repeat.

This clever loop lets you turn one colorless mana and a counter into an endless cycle of creature creation and sacrifice, fueled by Agatha's Soul Cauldron granting Ulasht, the Hate Seed's ability directly to Wildwood Mentor. Because Agatha's Soul Cauldron allows you to spend mana as any color, you can easily pay the activation cost using the proceeds from sacrificing your tokens to Phyrexian Altar. Meanwhile, Wildwood Mentor watches each new Saproling enter the battlefield to continuously replenish your counters, keeping the engine running indefinitely.