dross

the material in a metal that people do not want and they remove by heating the metal

his throne will be established by doing

The throne is a metonym for the power to rule. These words can be translated in active form. AT: "the king will establish his throne by doing" or "he will have the power to rule because he does" (See: rc://en/ta/man/translate/figs-metonymy and rc://en/ta/man/translate/figs-activepassive)