Sanderson has been stressing pretty heavily that cognitive shadows who are around for too long become completely driven by their core ideal, which in Kelsier's case is clearly 'survive'. So, if we're looking for the motive of the Ghostbloods - which Brandon said we were close to figuring out - I'd wager that's it?
So that's an interesting angle through which to look at everything the Ghostbloods have done so far. We know they were trying to find Urithiru (and stop Jasnah from finding it first), stop Gavilar from returning the Listener gods, and find and get information from the Heralds. They seem to deal in knowledge? So it seems like they're trying to become as Cosmere-aware as possible, in order to... what? Stop Odium from taking over the Cosmere? Just... live forever? There's always another secret.
