|"We survived the Fall of Danu Talis, we survived the Flood and the Age of Ice. And then, about three thousand years ago, a single metal worker, who had been crafting in bronze, began to experiment in the new metal. He was just one man - and yet he managed to wipe out an entire race of people and a way of life. Great change always come down from the actions of a single person ... I killed him. His action destroyed us. What else could I do? But it was too late. The secrets of Iron had been introduced into the world.”|
|— Hekate speaking to Nicholas Flamel about the tragedy of Iron in The Alchemyst|
One of the main reasons why Humani unknowingly triumphed over the Elder race was the Discovery of iron. In the series iron has the ability to nullify even the most powerful magic and its discovery signaled the end of the Elder Race's power in this world. Nicholas describes the inherent weakness of the Old generation Elders as an exploitable vulnerability implied by his constant presence of an iron-made black stone arrowhead with him.
Even though iron's natural resistance against magic and its poisonous effects in the presence of an Elder, The Next Generation posses a natural immunity against iron at a cost of loss of raw magical power compared to the Old generation Elders.