Firstly, about the Riddle stuff...The FF in RD & the FF in CC are obviously two different things governed by different rules.
Secondly, am I the only one who finds it just a little too convienient (or I guess you could say inconvienient) that the Masamune just happens to wind up in the Divine Dragon Falls (or wherever you believe that scene to take place) for Radius & Garai to find...I smell more of Belthasar's crafty handywork...
Hmm, I've always thought it's Dendoro Mountains (Espically since Radius, Garai, Viper and Zappa were stationed in Zenan). Then again, it could be DDF. However, it dosen't have to be Belthasar. I guess that manacial killer desired to get rid of the blade, with all the auras and ill-omens around it, and either someone really really powerful (Like, say, Crono?) placed it in Dendoro Mts\DDF\wherever, but was afraid to use it. He only carried it, never used it, perhaps even never made more then a couple seconds contact with it, and if he did touch it for lengthy perios of time his spirit would not succumb to the malice, because he never used it.
As for Riddel... Yeah, I know they work in the different terms. However, how can you explain the fact she has magical powers over the FF? Hmm?