FireStorm is the blacksmith HammerChain's apprentice in Bastion City. Bastion City is one of the only major cities in the Barrier Lands.
When he was just a little colt, him and MignightAura were walking in a field, and they came accross a mana battery. Mana batteries are magical weapons burried under Equestria. But thats when MA had an uncontrollable magical spark, as all young unicorns do. The mana battery and the young unicorn magic together casted a imensly strong teleportation spell, and sent the two foals to the barrier lands. He was then discovered and took in by an old blacksmith in Bastion City.
FireStorm was offered the choice to join the Northern Equestrian Legion to become a member of Special Opperations, or to stay a blacksmith with the old stallion. He earned his cutie mark by choosing to stay with his family in the forge. Since he was born in Equestria, he still got his cutie mark in the Barrier Lands, even though he was on the other side of the barrier. He used to assist in the forge, like go to scraps and find useable metal, but the old stallion was called to be the blacksmith of the elite legionaries. Now it's just FireStorm and MidnightAura at the forge.
He is constantly put to good use in the forge, making armour and weapons for the Legion. FireStorm works the metal into its desired shape, and MA keeps the fires of the forge burning.
REFERANCE: Major reference to Upheval: Breaking Point.