“We use electricity to power our homes, fires to warm the atmosphere, drugs to fuel medicine, and ice to cool us down against the unbearable heat. These knights had all of that; individually, but they could control such magic on a whim. Nobody knows how they managed to attain their powers, with some saying they had slain the mightiest of beasts using their respective elements. Now that they’ve come together again, they’ll be sure to overwhelm their opponents in a crashing maelstrom.”

Castle Crashers' knights pretty much act as skins, but they have different movesets pertaining to their respective powers (Red uses electricity, Orange uses fire, Green uses poison, and Blue uses ice). They also might have different weapons, even if they all have the same standard sword and shield. As for their story here, much like S'Asshole and Larry, they were from the past. They don't exactly care for why they're here, as they've been itching for a fight after so long. They'll get one, though it won't involve saving princesses this time around, to their collective relief.