Cauldron of Souls + Dross Scorpion + Biotransference + Phantom Train

Cauldron of Souls

Dross Scorpion

Biotransference

Phantom Train

How it works

1. Activate Cauldron of Souls by tapping it, giving the creature with bloodthirst persist until end of turn.
2. Activate Phantom Train by sacrificing the creature with bloodthirst.
3. When the creature dies, its persist ability and Dross Scorpion trigger.
4. Resolve the persist trigger, returning the creature from your graveyard to the battlefield, which enters the battlefield with at least one +1/+1 counter on it due to its bloodthirst ability.
5. Resolve the Dross Scorpion trigger, untapping Cauldron of Souls.
6. Resolve the Phantom Train ability
7. Repeat.

This ingenious loop transforms your creatures into a self-sustaining engine by turning them into artifacts via Biotransference, allowing them to fuel Phantom Train's sacrifice ability while constantly resetting their own mortality. Each time your creature dies with persist granted by Cauldron of Souls, it returns to the battlefield with a -1/-1 counter, but thanks to its bloodthirst ability entering alongside these mechanics, that counter is immediately neutralized by a +1/+1 counter. Meanwhile, Dross Scorpion watches the carnage as an artifact creature dies and untaps Cauldron of Souls, letting you repeat the entire process to generate infinite deaths, enters-the-battlefield triggers, and a massively pumped Phantom Train.