This ingenious loop relies on Warren Soultrader to fuel an engine where Gravecrawler repeatedly sacrifices itself for a Treasure token, which in turn provides the black mana needed to recast the skeleton straight from the graveyard. While the Soultrader's activation costs you 1 life each iteration, Healer of the Pride effortlessly offsets that cost by granting you 2 life every single time Gravecrawler enters the battlefield. Because Gravecrawler's ability allows it to be cast from the graveyard as long as you control another Zombie—a creature type that Warren Soultrader happily shares—this closes a perpetual loop that generates infinite enters-the-battlefield triggers, death triggers, and lifegain.