Medusa was a harsh, unwelcoming planet inhabitated by a tough and stoic people. Ferrus would not join these tribes, as many of his brothers did. Rather he would he seek out physical challenges, to make himself stronger and more resilient. These tests ended with his battle against [[Asirnoth]], the Great Silver Wyrm, a metallic beast impervious to harm and Ferrus had to drown it in magma to kill. The melted flesh of the worm fused into Ferrus' flesh, giving him the true metal hands his Legion would take its name from.

Ferrus now returned to the tribes and started lecturing to them on technology. The clans advanced at a stunning pace and Medusa prospered. But Ferrus took care to leave the inter-clan rivalry and fighting by never taking sides, as he saw the competition between them as healthy and good.

The Emperor eventually came to Medusa, and Ferrus Manus tested himself on him as well, in a cataclysmic battle that is said to have laid waste to entire mountains. Finally having found someone equal , Ferrus accepted the Emperor as his master and took command of a legion of [[Space Marines]].

Thousands of planets would fall for to the remorseless [[Iron Hands]] under Ferrus' leadership. Each weak link in humanity was to be purged if mankind was to grow stronger. Scholars spoke of the wave of piety and faith that spread before of the Iron Warriors; with many planets suddenly motivated to look into themselves when they heard that the Iron Warriors were approaching.

The Iron Hands was one of the loyal legions the Emperor called to [[Istvaan V]]. Given the large distance , Ferrus Manus took the Legion's fastest ships and departed only with his veteran chapter. They were all lost during the battle, struck down by the traitor legions.