Steelhoof is very unusual among most tumblr ponies, as he is no longer sees himsef as a pony. During some horrific accident he can unfortunately not remember, Steelhoof is made almost entirely out of metal, his brain being the only organic component.
Because of this, he feels alone and isolated, despite the fact that this is rarely the case and there are ponies who care about him.
Steelhoof is a deeply unhappy pony, as he feels that he is a monster and that he should never have existed. As a result of this and his augmentation, which has left im with brain damage, he is emotionally unstable and unable to remember his life 'before Steelhoof'. He considers himself two seperate entities, the pony he was before, who he frequently refers to as 'the old me', and Steelhoof.
His special talent is in protecting ponykind from harm to the best of his ability, but it soon became a curse. Every time a pony dies, anywhere in the world, Steelhoof feels as if he died inside, a terrible burden on his life.
Steelhoof has no real recollection of his birth, or anything much about his family, besides the odd spoken word or comforting touch. Around five years prior to his becoming an ask blog, he woke up in a castle, just north of Stalliongrad. This was where Steelhoof himself was created, for a single purpose. Steelhoof was created to kill, but he had woken too soon for the full brainwashing to take place. He fled the castle, and remained on the run for quite a long time afterward.
Due to his strength and stamina, much greater than that of any pony, he was easily able to find work as a labourer. Unfortunately, his great strength took him a long time to understand, and in theat time, just a friendly pat on the back could end with a broken bone or worse.
Also, due to his instability, anything that caused him to fly into a rage usually caused him to be violent, often to the point of accidental murder or ponyslaughter. As a result, he remained on the run for several years, always with an eye over his shoulder, always expecting his puruers to catch up.
Also, the killer instincts that he was created for plagued him constantly, eventually boiling over into an inescapable urge to kill something. He had wanted to die almost as long as he could remember, but in these states he became even worse. He would take on the most powerful creature he could find, and try to beat it to death with nothing but the small blades that curve around his hooves. To his surprise, this method of stress relief was surprisingly effective, and Steelhoof was also able to discover his armour's self healing mechanism that repaired damage, to an extent. However, it was unable to fix circuitry problems, for which he had to visit a mechanic. Eventually, he came to Ponyville, and the friendly villagers within disarmed him and he decided to stay.
There, he met White noize, a pegasus stallion who also had a fighter's mentality. Soon, Steelhoof had his first true friend, and he began to attempt to setle down. Then, he met other ponies like Demonheart, and soon had a number of friends to rely on in times of need. He also met Sugar cream, a petite pegasus mare with an talent in love. Much to Steelhoof's surprise, they found themselves falling in love with each other. Their love blossomed, and for a time, Steelhoof found himself happy. However, Sugar cream was soon taken from him, and Steelhoof fought to get her back, almost dying in the process. Feeling as if he betrayed his cutie mark, he exiled himself for a time, and has rarely smiled since, believing that nopony will ever love him again. Even now, he believes this, rarely bothering even to talk to the mares he finds attractive, as he believes that rejection is inevitable.
(Disclaimer - White noize, Sugar cream and Demonheart do not belong to me. They belong to their respective owners and noone else.)