This elegant loop creates a perpetual motion machine of pain and healing once you get the ball rolling. It all starts the moment you gain life, which causes Enduring Tenacity to trigger and make an opponent lose life. That loss of life immediately activates Exquisite Blood, driving you to gain life right back and restarting the entire cycle. Because Enduring Tenacity also has a built-in safety net that returns it to the battlefield as an enchantment if it ever dies as a creature, your engine is remarkably resilient against removal.