In both ancient Greek and Latin "Hephaistos' breath" is a poetic way to say fire and often the god's name was used as a synonym for the element. Even iron, "hardest of all things", is softened by fire and melts through the strength of #Hephaistos.
I wrote a whole article on #Hestia and Hephaistos, the gods of fire in #GreekMythology which is free to read on my website:
