Living metal was a magical creation that came about through Daja Kisubo.
For her first accidental living metal creation in the autumn of 1039 KF while they all were at Gold Ridge, her ambient smith magic had combined with the specific magics of her foster sisters and brother. Although the main influence--doing something with metals--was Daja's, the initial creation also had parts of the other children's magic in itself. Its resembling a vine was clearly influenced by Briar's plant magic while the intertwined branches came about as a result of Sandry's thread magic, and the general twisting of the branches like a cyclone was Tris's influence. The vine not only resembled a real plant but it also grew from absorbing further metal. After some time it even grew roots.