Untrusting at first, but he commands the loyalty of his subjects. Once you convince him to fight for you, he should prove to be valuable ally needed.
— Game Description
Arthur is a unique troop, which means there can only be one Arthur at a time. Arthur and Henry are the perfect units for attacking King Deaditie, they are powerful and make quick attacks. If the Wiseman joins them, and some Armored Guards the King Deaditie won't be able to touch the book.
Arthur's weapon is his sword, a heavy sword but quick sword. Arthur attacks very quick compared with other units. He always comes with two additional archers for helping him.
You don't have to include the archers in your army in order to Arthur to come with them.
Arthur is a Hero, he appears magically in a wave and then joins your army.
Arthur and the armored guards seem like the same thing, but they are very different.