The King is tired of watching his army battle from his ivory tower, so he's decided to join the party! In his own words, "Verily, if I am to continue hosting these splendid banquets, I must needs take a brief respite to stretch mine legs."
However, you're the Commander here, so the decision on whether you choose to have The King in your star line-up or not is all yours! Here's a couple of things that will help you decide:
He's a pretty solid attacker!
No one can cheer up your Squads like The King: He'll boost their damage before unleashing a lance thrust that decimates his enemies. A power move to show 'em who's the ruler!
Make sure you place The King well surrounded by his troops. He'll feed off that energy. The more allies around him, the stronger he becomes.
Please note that The King will only accept orders from you and no one else INSIDE the battlefield. Try to get him to follow instructions at any other time and it may be the end of you as a Commander.