You will have to go through a large number of waves of enemies, where at the end you will find their boss - the King.
Warriors - the master sword, they can hurt you only if you let them get too close.
Archers - professional arrows while you will be distracted by Warriors who will try to approach you as close as possible - the Archers will send you a hail of arrows.
Mages - few can learn magic, so the Mages - an elite unit of the king. They release clots of magical energy that will haunt you and try to hurt you, but bullets from your weapons can break them easily.
During the passage of waves, you can improve your weapon - increasing its damage or rate of fire.