Here "king of the North" includes his army also. AT: "The army of the king of the North will come" (See: [[rc://en/ta/man/translate/figs-synecdoche]])
# pour out earth for siege mounds
This refers to the piling up of earth in order for soldiers to reach the height of city walls in order to attack them. Soldiers and slaves would put loose earth in baskets, carry them to the right place, and pour it out in order to raise the mounds.
# fortifications
walls and other things built to defend a city or fort from enemy soldiers
Here "destruction" represents the power to destroy. Also, the power to destroy is spoken of as if it were something that someone could hold in his hand. AT: "he will have power to destroy anything" (See: [[rc://en/ta/man/translate/figs-metaphor]])