Traitor Ghost helps fight Kudgel

I thought I was going to have to fight the four ghosts at the South Idol alone so I got the traitor ghost (I could only summon one). When I arrived at the South Idol there was another pirate there and his fighting helped us defeat the four ghosts fairly quickly. With some time left on the clock the traitor ghost followed me to Dr. Bellfrog and he lasted through about half of the fight with Kudgel.