While the stats it gave and its passive effect Calm The Beast were not all that impressive, the Leaf of Serenity Necklace stood out because of one thing—it granted magic power.
Magic power was a highly sought-after stat for magic casters. That's because it did not only increase one's damage but the entirety of a magic caster's spells. For example, take it that one's magic power was at 10%. If that were the case, a spell that had 100 damage, a 1 second stun, 1 second cast time, and a 10 second cooldown, would suddenly become a spell with 110 damage, a 1.10 second stun, 0.90 second cast time, and a 9 second cooldown.
Every aspect of a magic caster's spell would be influenced by magic power. On the surface, it only seemed like a small 10% increase, but in reality, the power boost one received to their overall strength was much larger than a mere 10%.