Yarus, Roar of the Old Gods + Karlov Watchdog + Fateful Handoff + Phantom Train

Yarus, Roar of the Old Gods

Karlov Watchdog

Fateful Handoff

Phantom Train

How it works

1. Donate Karlov Watchdog to an opponent.
2. During the opponent's turn, activate Phantom Train by sacrificing a face-down creature you control.
3. When the creature dies, Yarus's second ability triggers, returning it from your graveyard to the battlefield face-down as a 2/2 creature, and then not turning it face-up due to Karlov Watchdog.
4. Resolve the Phantom Train ability.
5. Repeat from step 2.

This peculiar loop turns Phantom Train into a relentless sacrifice engine, feeding on your own face-down creatures to continuously grow its own power with +1/+1 counters. The crucial trick relies on giving away Karlov Watchdog with Fateful Handoff: because your opponents now control the Watchdog, its static ability prevents permanents from being turned face up during *your* turn, cleverly overriding the usual "then turn it face up" safety clause on Yarus, Roar of the Old Gods. This leaves Yarus free to repeatedly return your sacrificed face-down creatures to the battlefield safely face down, generating an endless stream of death, sacrifice, and entry triggers.