When the heroes assist the remnants of Laurent's Amazon army in retaking the castle, Bill and Ben engage the heroes in combat. After they lose, Belladonna orders the Nevarl forces to retreat.
Later, when the heroes are attempting to reach the Mana Stone of Fire in the Valley of Flames, Bill and Ben appear once more to prevent them from achieving their goal. After they are defeated for the second time, Belladonna is forced to sacrifice them in order to release the energy of the Fire Mana Stone.
Bill and Ben always start off by combining into one Master Ninja. They have several powerful attacks that they will often use to counter any sort of magic used against them. Their special ninja techniques are especially lethal because each one will lower the heroes' stats. After taking a considerable amount of damage, Bill and Ben will split up into two separate ninjas, both with approximately the same power as before.
In essence, Bill and Ben are comparable to Hawkeye's Ninja Master (Dark-Light) class. Having Kevin and/or Duran is especially helpful as Duran can take away plenty of HP, and Kevin even more so with his ability to transform at night, on top of having Pressure Point, as well as an exploitable glitch that gives Kevin even more power if he gets hit in werewolf form.
Circle of Mana
Bill (Green) and Ben (Red)