Ah. The Orb of Sucellus is definitely not a piece of the GodSlayer. I forget which piece is where, but I know that one piece is found in a Doviello city (their capital, iirc), one in an Illian city (near the center of the map), and one is found in the volcano in the center of the tropical, panther-filled peninsula in the upper right hand corner of the map. I haven't played in a while (and cheated a lot when I did), but I believe that you must defeat Malus and take his ship in order to reach the island, although when you take the godslayer piece it will cause all volcanoes to erupt and turn into (passable) craters, including the one that was blocking access to the peninsula from the the walled in region of the map where you'll likely find Hati and Mokka. Oh, I think you might be able to get it too if you can capture Fiacra and use her to explore the peninsula. The event that lets you free the blade (I think that piece is the blade) and turns volcanoes to craters is triggered by having that particular tile become visible. Oh, I also think that you could theoretically wait for a blizzard to turn the water separating the peninsula from the mainland to ice, and then cross without a boat.