Continuity mistake: When you first meet the Doom Dragon on top of the Mars Lighthouse, its red head is on the left. When you actually battle the Doom Dragon, its red head is on the right. You see it both times from the front, so it's not an angle issue.
Plot hole: Even if you've acquired Piers's ship before visiting Garoh (a city populated by werewolves), when you first set sail in Piers's ship, Sheba will say, "We've already met werewolves."