By using Zur, Eternal Schemer to animate All Will Be One into a creature, we unlock the missing piece of a devastating loop, granting it the deathtouch, hexproof, and crucial lifelink provided by Zur's static abilities. Once you attach Light of Promise to that animated enchantment, any initial spark of life gain triggers Light of Promise to place a +1/+1 counter on All Will Be One, which in turn fires off All Will Be One's damage ability against an opponent. That damage grants you life thanks to lifelink, restarting the cycle and creating an endless loop of infinitely growing counters, damage, and life.