The Steel Saints was characters created by TOEI to Bandai sell action dolls of the Saint Seiya series (created only to this goal [sell dolls]).
History and "powers"
The steel saints were originally 3 young boys, that trained by Doctor Asamori, a scientist of Graad Foundation. To help Saori Kido, Mitsumasa Kido (that have not many saints in the Saori's side) ordered to Asamori builds clothes that have hi-tech weapons, and can be used by any guy as a war weapon, with no strong Cosmo. These cloths, like the Black clothes, don't have a life, and with no it, the steel saints are normal strong dudes, and can't fight against aover power being. But, the steel saints only must help the saint is in the battle, because they are not strong to have a battle alone against an official member of a good army.
The main 3
In the series, Sho (air element), Daichi (Earth element, and the youngest of the three) and Usho (sea element) was trained to getstrong muscles (as a normal fighter of martial arts) and used the steel clothes in the first time, to helps Hyoga in the fight against Babel; after, they helps Shiryu in the Algol. They help Seiya in the fight against Aracne. So, they never defeated an enemy, but only helps the true saints to defeat the enemies.
After Kurumada asks to TOEI to remove these saints, like other fillers, the still saints were never remembered. Only for nostalgia, in Saint Seiya Omega, they returned. After, in Soul of Gold, fillers like the God Warriors returned too, so, TOEI actually, wants rebirths itsfeelers.
Dr. Asamori is not a steel saint, but was the creator of their clothes, and them teacher (of the main 3). He was a loyal servant of the rich Mitsumasa Kido; after his death, Asamori tried give up, but his loyality did him continues the project, and end it, after nights awake; the steel saints only have been able to fight, when Babel arrives in the Japan (when they get ready to fight, already goes fight to help Athena).
Omega Steel Saints
After Hades arc, Nachi and Ban, leaved his offices as saints, and trained youngs boys to become new steel saints, with various steel clothes (like a normal armor, the Graad Foundation built various and gived they to the apprentices some clothes, and like heavy weapons, various were kept in reserve); all the new steel clothes was similar between theirselves (Erna put a adhesive in his cloth), only ranging the colors. Ban and Nachi got steel clothes that was similar to their former bronze clothes. Jabu and Geki gets a stell clothe later too. All the steel saints goes to Pallas Belda, and was humiliated there, because their weakness (they are most weak than the quartenary pallasites, and only must helps the saints in the battles). These new generation is most weak than the Bronze Saints. The 3 main saints returns too and fight against strong pallasites.
Erna had a strong cosmo, althought never become a official saint. But, his wishes was to be a true saint of Athena, and searched by he constellation. Erna ever put adhesives in his cloth, and the last was a shooting star adhesive. After his best friend (Subaru) returns, the pallasites attacked the camp, and Eruna was killed.
Subaru is a memory-changed version of Saturn (main villain), so, only "Subaru" will be described.
Saturn changes his form to a human to understand the humans; his human form was named Subaru, and don't remember that he is Saturn, and because this, tought he had a normal childhood, but don't remember his childhood because memories defects (but, Subaru was born a teenage boy, probably during Mars's fight against Athena, so, no one met him for a long time).
Subaru, influenced by Saturn, wished to be a god, and goes randomly to Steel Saints trainig camp (he was hungry, because was born with no eat nothing), and there, he was care for Nachi and Ban, in exchange to became a steel saint, but, he never served Athena, and only became a still saint to be as strong as a god and to be a place to live. When know about Kouga fights against Abzu (Kouga killed the evil god), wished defeat him to be a god, and get away from the camp to fight against Kouga. But, after the Pallasites attack, Subaru momentarily gives up of the battle against Kouga, and follow him to help in his journey to defeat Pallasites, free citys and get allies.
After Erna death, Subaru used his cloth and after the destruction of this cloth, Subaru need a new cloth, and was choosed by Equueleus cloth, and become a bronze saint. He become Saturn after the Pallas surrender.
A steel saint that his wife and son was killed by martians in battle against Mars. After a god kill his family, Kerry never trust in any god again, and only fights to Athena, because she is the best way to promove peace;; Kerry always accept the fact the fact that he is a weak class of saint, and no important function. But, Kerry was kiled after helps Souma to defeat Loge.
Emma was a girl that goes to Pallasite, and hoped be a important function there. But, when she see the steel saints murder, she perceived she and the steel saints are weaks saints. She is very sentimental, so, had a identity crisis. But, in the battle against Loge, she accept her function and helps Souma (as always did the steel saints) to defeat Loge, but see another weak steel saint dies: Kerry.