Dross Scorpion + Elemental Mastery + Encroaching Mycosynth + Phantom Train

Dross Scorpion

Elemental Mastery

Encroaching Mycosynth

Phantom Train

How it works

1. Activate the creature with Elemental Mastery attached by tapping it, creating a number of 1/1 Elemental creature tokens with haste equal to its power.
2. Activate Phantom Train by sacrificing an Elemental.
3. When the Elemental dies as an artifact due to Encroaching Mycosynth, Dross Scorpion triggers, untapping the creature with Elemental Mastery attached.
4. Resolve the Phantom Train ability.
5. Repeat.

This loop turns an ordinary tap ability into an engine of endless destruction and growth by turning your entire board into a machine shop. Thanks to Encroaching Mycosynth, every creature you control becomes an artifact, meaning when you feed your tokens to Phantom Train to pump its counters, Dross Scorpion sees an artifact creature die and immediately untaps the creature enchanted by Elemental Mastery. This lets you tap the enchanted creature again to flood the board with new haste tokens, creating an endless cycle of sacrifices that fuels Phantom Train infinitely.