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

Yarus, Roar of the Old Gods

Karlov Watchdog

Donate

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 clever little engine turns Yarus, Roar of the Old Gods and Karlov Watchdog into a clever lock-and-loop by exploiting how replacement effects interact with the graveyard. You hand your opponent Karlov Watchdog using Donate so its static ability—stopping permanents from being turned face up during *your* turn—instead prevents your opponents from turning things face up on theirs, which crucially blocks the final half of Yarus's recursion trigger. Then, by sacrificing a face-down creature to Phantom Train during your opponent's turn, Yarus triggers to return that creature to the battlefield face down, but stops right there before it can flip upright. Because the sacrifice and recursion happen entirely on the opponent's turn (dodging the Watchdog's restriction), you can loop the cost of Phantom Train indefinitely to generate boundless deaths, leaves-the-battlefield triggers, and massive +1/+1 counters on your Vehicle.