The Dark Knight, shortened DK, is the most popular character, most likely because of its focus on pure physical combat. Dark Knights have naturally high HP, great weapons, and the best armor. This makes them well-equipped to be the primary attacker in a party, and coupled with the "buff" of an Elf, is a mighty force indeed. Lower level DKs generally apply their stat points as they "level up" to Strength with some stat points applied to Agility. Strength is a very important stat to them because it helps them with their attack and their equipment.
After completing the game’s first quest, the Dark Knights are promoted to Blade Knights, which have stronger stats and are able to use greater weapons and armor than those of Dark Knights. They can also learn new skills a Dark Knight can't learn, such as Death Stab (which requires level 160)and Rageful Blow (Which requires level 170). Also notice the character's change of hair from black to blond and long sleeves and pants.
Beginning with MU Online Season III, the Blade Knights can evolve to Blade Masters after completing the three-part quest. They can use all the armors and weapons for Dark Knights and Blade Knights. Moreover, there are 3rd Level Wings (Wings of Storm) with special options. blade master also have new sets and weapons...