Activate Warren Soultrader by paying 1 life and sacrificing the persist creature.
When the persist creature dies, its persist ability triggers, returning the persist creature from your graveyard to the battlefield with a -1/-1 counter on it.
When the persist creature enters, Lifecreed Duo triggers, causing you to gain 1 life.
Resolve the Warren Soultrader ability, creating a Treasure token.
When the Treasure enters, Mm'menon triggers, putting a +1/+1 counter on the persist creature.
Repeat.
This clever loop turns a persist creature's self-resurrection into a self-sustaining engine, fueled by Warren Soultrader to constantly churn out sacrifices and Treasure tokens. As those Treasures enter the battlefield, Mm'menon, Uthros Exile steps in with a +1/+1 counter to instantly cancel out the creature's -1/-1 counter, keeping it ready to die again. Meanwhile, Lifecreed Duo watches the creature repeatedly return, padding your life total so you can safely keep paying the Soultrader's cost indefinitely.