Ya, that's the one thing that makes me doubt it's the black sphere. He was always talking about being honorable and the Way of Kings, I can see how that could be something he let slip. Especially when taken with the 2nd quote below, what was he going to do with the sphere, try to soulcast it maybe (fabrial wise)? But how does something like that slip out when you haven't told your closest allies? On the other hand, he was noticeably different to everyone...always talking of honor and the book.
Just listened again,
killed him..."in a desperate gambit to stop the parshendi gods from returning. Well...that hadn't worked out."
"if he had lived to do what he told them that night, all would have been lost." are the quotes she says about him.
Listening to the first quote, it's BS that stresses that word, and it's hard not to draw the conclusion that the parshendi gods returned anyways. Which seems slightly contradicted by the second quote, but...
Something cool to consider with the quotes above? When Szeth murders Gavilar...
Too late for what? So maybe he was talking about the Ghostbloods or something he was going to do in regards to them that set the parshendi off. So Szeth is too late, Gavilar has already done something...which coincides with the assassination failing to fully prevent Gavilar from bringing back the parshendi gods, which would match up with the first quote from the new reading.