This clever loop starts by casting Feign Death to place its protective revival effect on Izzet Chronarch. You then feed Izzet Chronarch to Phyrexian Altar, sacrificing the creature to generate the black mana needed to recast the spell. Because Izzet Chronarch enters the battlefield with its signature trigger, it immediately pulls Feign Death right back out of your graveyard and into your hand, setting the stage to repeat the entire cycle endlessly.