Eirdu, Carrier of Dawn // Isilu, Carrier of Twilight + Phyrexian Altar + Butcher Ghoul

Eirdu, Carrier of Dawn // Isilu, Carrier of Twilight

Phyrexian Altar

Butcher Ghoul

How it works

1. Activate Phyrexian Altar by sacrificing Butcher Ghoul
2. When Butcher Ghoul dies, its undying ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it.
3. Activate Phyrexian Altar by sacrificing Butcher Ghoul
4. When Butcher Ghoul dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it.
5. Butcher Ghoul enters and dies as a state-based action due to having 0 toughness. Its undying ability triggers, returning it from your graveyard to the battlefield with a +1/+1 counter on it.
6. Repeat from step 3.

By flipping Eirdu, Carrier of Dawn // Isilu, Carrier of Twilight into its Isilu, Carrier of Twilight face at the start of your turn, you grant Butcher Ghoul the persist ability to complement its native undying mechanic. Sacrificing Butcher Ghoul to Phyrexian Altar generates mana while triggering its dying triggers back and forth. Because the +1/+1 and -1/+1 (or -1/-1) counters cancel each other out upon subsequent deaths, the Ghoul gets caught in an infinite loop of returning to the battlefield, feeding your engine an endless stream of sacrifice triggers and colored mana.