What you see is Ragnos fading into his tomb...Odan just mentions his nightmares of the empire, any ALLUSIONS to Ragnos are nonexistant. Plus, the JEdi didn't even KNOW OF any Sith Empire, 1 and 2? Ragnos didn't pass...he just went into his tomb...and wouldn't the passing of a powerful and evil spirit be a GOOD thing?