The gold-veined white marble came from the tower's walls while the shield and the equipment of the Demons had been Forgemastered by the Factory floor.
Also, despite what the living legacies believed due to the seemingly endless stream of magical resources, Lith's means were actually limited to what he had stored in the pocket dimension, the Crucible, and the Mines.
Yet the tower's Workshop could conjure whatever was contained in its vaults infinite times. The Workshop would create copies of the magic crystals and metals identical to the originals that the Factory would instantly Forgemaster into enchanted artifacts.
The moment one of its creations was destroyed, the tower erased the copy and created a new one. Then, the Factory would Forgemaster an improved version of the artifact by accessing the data collected by the Eyes during its use.