Coldsteel began as part of the cyborg known as Coldstone, who was in many ways a modern-day Frankenstein, the result of Xanatos Industries creating a cyborg out of the remains of several gargoyle statues shattered during the Viking raid: however with time Coldsteel would become a separate being in his own right.
Coldsteel began life as a Gargoyle known as Iago, who was decidely more traitorous than most of his kind - he tricked his brother into believing that his mate was having an affair with Goliath and caused his brother in turn to fight Goliath in a rage.
Yet Iago's lies were exposed and he was temporarily banished from Castle Wyvern as a result.
Later both he, his brother and many other Gargoyles were shattered in the Viking attack and would remain that way for centuries - until David Xanatos had Iago's remains collected alongside those of his brother and his brother's mate.
Using advanced technologies Xanatos created a cyborg known as Coldstone using the body parts of the three Gargoyles, as well as considerable cybernetic enhancements - however when a computer virus infected the cyborg Iago's malevolent spirit was able to take control and began to once again battle against his brother, this time by forcing his brother's mate to merge with him.
Goliath, using Virtual Reality to explore Colstone's mind, and the other two gargoyles within Coldstone managed to defeat Iago and reduce his power.
Iago remained with the other two gargoyles inside Coldstone's mind and when Macbeth and Demona stole Coldstone and reactivated him, Iago immediately took control and helped them battle Goliath and the Manhattan Clan, not knowing that the battle was merely intended as a distraction so that Demona and Macbeth could steal the Grimorum Arcanorum, the Eye of Odin and the Phoenix Gate without Goliath noticing. When Iago's two rookery siblings decided to help Goliath, they took control over the Coldstone body and kept Iago out of control.
Later, Xanatos had two new robot bodies built and planned to transfer the souls of Iago and Desdemona into them as a way to express his gratitude to Goliath for helping rescue his son, Alexander Fox Xanatos, from Oberon. Xanatos' assistant Owen Burnett/Puck instructed Alexander (as a part of a deal with Oberon to teach Alexander magic) to first transfer the souls of Othello, Desdemona and Iago into Broadway, Angela and Brooklyn's bodies and then, after making the gargoyles think that the robot bodies were a Xanatos scheme to fight them, impressed Iago enough for him to willingly be transferred into the robot body called "Coldsteel". Coldsteel blasted off, only to be followed by his rookery siblings, Coldstone and Coldfire.
Xanatos summoned Coldsteel to the Scarab Corporation to acquire his services in stealing the Stone of Destiny.
Coldsteel agreed to work with Xanatos if he would turn off the homing beacon that summoned the android. As he agreed, Coldsteel attacked Hudson.
Coldfire damaged Coldsteel so significantly that he had to abandon his efforts and flee his sister in order to make repairs. As a reward for his troubles, Xanatos disabled the tracking chip installed in his systems.
- Coldsteel is another name for Iron, a metal traditionally believed to be harmful to the Fay (or fairy folk) - this legend would appear later in the series with the creation of the Iron Clan.
- the battle in Coldsteel's mind is loosely based on the story of Othello by Shakespeare.