Originally Posted by
Malakh
Well it is known that on Pandaria not only did the Titans completely killed off an Old God (Y'Shaarj) and thus releasing the Sha, but also that one Titan "fell".
Now, if a Titan falls, it isn't exactly known if he dies, weakens, "deactivates" or becomes similar to Sargeras (he is the "fallen titan" after all). Although that last point of becoming like Sargeras isn't that plausible.
BUT, a fallen Titan could also mean that he is just really weakened, and thus could've been imprisoned, used and siphoned energy off of by the Mogu and the Thunder King himself.
The creation of the Divine Bell "from maker's flesh, shaped by star's fury" etc. indicates the involvement of a real Titan and not just one of their creations. If the Mogu had indeed a fallen Titan imprisoned, then the Korune spellweavers who brought the bell to Lei Shen, could've experimented on the Titan and in the end being successful in creating a weapon off of it.
With the involvement of the Sha it could also be, that the Titan "fell", because it was dominated by the seventh and last Sha, therefore needing to be imprisoned to stop wreaking havoc all across Pandaria. The Mogu found him and used him to fuel their own plans and to conquer all of Pandaria.
Now, when Lei Shen dies, and we venture into Ra-Den's prison, we free him, or at least free the seventh Sha in the process of putting an end to him. And we all can see now whom this last Sha would try to consume and take over, our beloved Son of Hellscream.
He is after all trying to master the Sha and searching for new ways to do so after the Bell is now lying in pieces.