For those of you who don't know, a Trapezohedron is the best Emblem/Demon symbol (Dark Rosary, Imperial Seal, etc.) in the game, and through normal means the only way to get one was off of a legendary Arcadia's Item God. This is 10000 times easier for people who can't yet handle the Land of Carnage.
After the post game, use a power level guide to make some strong characters that will get you through all of the bonus/makeup exams until you reach Baal (He's got 1,000,000 for every stat...) At this point START the Raspberyl story by talking to the yellow masked hero in the Base. When you get to the third fight take your strongest character/theif and work on over to Master Big Star. If you check his inventory he has one equipped and since he's only level 1000 something it's a piece of cake to steal!
Hope thishelps some of you who are having trouble finding legendary Arcadias, I know I was!
One last thing, at this point I did have the LoC unlocked, but I don't think that should have any effect.