This clever little loop uses Phyrexian Altar as both the executioner and the battery, turning the mana from your sacrifices into the exact fuel Reassembling Skeleton needs to crawl back from the graveyard. While the Skeleton is busy looping between the battlefield and the bin, Tormod, the Desecrator watches cards leave your graveyard and rewards you with a steady march of Zombie tokens. Those tokens aren't just extra board presence either—they can be fed right back into Phyrexian Altar to generate the extra mana needed to sustain the engine indefinitely.