Ferrus Manus, also known as "The Gorgon" name given to him by Fulgrim, is one of the Emperor's 20 children. Primarch of the Emperor's 10th legion of space marines: The Iron Hands.
Found upon the planet of Medusa by a local sect of Adeptus Mechanicus. Upon Medusa during his youth, Ferrus with his bare hands killed a great metallic beast whose blood stained unto his arms, which rendered them as hard and durable as any metal material. Later in his life Ferrus gained a fierce reputation as a cold and relentless warrior and craftsmen, who purged the weakness of all the tribes of Medusa, allowing only the strong to live and thrive.
Upon encountering his father for the first time, his sheer commanding presence alone made Ferrus bow down and swear his allegiance.
Later after being reunited with his father the Emperor of Mankind, he made quick friends with Fulgrim, the Primarch of the 3rd Legion, who he later made a blade for.
Ferrus also formed a close bond with Vulkan, the Primarch of the 18th legion, who also was an exceptional craftsmen.
Fulgrim and Ferrus remained very close friends up until the Horus Heresy where Fulgrim was ordered by Horus to kill Ferrus, his best friend.
Ferrus and his legion gained a reputation for their iron will and resolve, their disdain of weakness and their expertise in technology.
However this disdain for weakness was taken to the extreme, with nearly every member of the legion replacing nearly every part of them selves with mechanical argumentation and replacements, as to purge the weakness of the flesh. Ferrus however took a great disliking to this ideology. Ferrus thought his metallic arms were a bad example, so he wanted to undo what had been done to them so that he could show his men that they should trust in their own abilities and not machines and metal.
At the dawn of the Horus Heresy, Ferrus was approached by Fulgrim who tried to convince him to join him and Horus. This how ever only enraged Ferrus which led to a fight.
Later in the Dropsite Massacre, Ferrus and Fulgrim came toe to toe once more, except this time Fulgrim got the drop on Ferrus and decapitated him, an act which would haunt and torment Fulgrim forever.
Ferrus' skull was offered to Horus but was later recovered and given to his legion that is now held as their most revered relic.