Verified answer

You have to obtain the Seven Fell Arms before you fight Duke. If you've already beaten the game then I don't think they'll let you. Once you pick up all the Fell Arms you should be able to unlock the final battle. At any rate, most of the Fell Arms are kind of useless, and they don't really have any special skills or anything. They have attack abilities far worse than most of the other weapons, like Last Fencer or anything. Truth be told I'm not sure. All you have to do is walk back to the top of Tarqaron to find out... but I'm quite sure it's not possible.

You can either reload the game from right before you fought Duke to get the arms, or you can replay the whole game but bring over all the items from your currrent playthrough using the Grade Shop.

Tales Of Vesperia Fell Arms

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tales of vesperia: fell arms, how to unlock there power?

Iv got all seven fell arms and i know that you have to fight duck in his third from to unlock there power but i cant find him or trigger the fight with him.is there something else you need to do to allow the fight with duck in his third form or is it to late since i beat the game once before...