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, Essence Warden 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 ingenious loop transforms a humble sacrifice engine into a self-sustaining engine of life and wealth by cleverly pairing Warren Soultrader with a creature boasting the persist mechanic. As you feed that creature to the Soultrader, its sacrifice is immediately cushioned by Essence Warden turning every return to the battlefield into a net-neutral life total, neutralizing the cost of the Soultrader's activation. Meanwhile, the resulting Treasure token enters and triggers Mm'menon, Uthros Exile, whose passive artifact-watching ability places a +1/+1 counter on your persistent creature to continually cancel out its accumulated -1/-1 counters.