Basically, the knife was specifically to kill Jezerien
WeiryWriter
You've stated that the sapphire in the knife that Moash used to kill Jezrien was specifically for Jezrien. Was it that for actual mechanical reasons, or more of a symbolic gesture?
Brandon Sanderson
RAFO
Skype Q&A (Oct. 8, 2018)
And his soul is trapped, not destroyed
Questioner
Moash killed a god? One of the Heralds?
Brandon Sanderson
He did. One of the Heralds. And trapped his soul so he couldn't be reborn.
Questioner
That's what it is. Trapped his soul, didn't actually kill him?
Brandon Sanderson
It's killed him-- It was like, extra killed. The Heralds are bound to a cycle of rebirth that happens-- that they wanted to make sure didn't happen that time.
Idaho Falls signing (Dec. 29, 2018)
And we got that the saphire was for Jezrien
Hoidonalsium
Is the sapphire in the white-gold blade specifically for Jezrien?
Brandon Sanderson
Uh, yes.
Hoidonalsium
Do the gems swap out, or are there different weapons?
Brandon Sanderson
I'll RAFO that one.
Hoidonalsium
Are they Dawnshards? Or blades of Odium, like Honorblades?
Brandon Sanderson
Those are not Dawnshards. Good question.
Oathbringer Glasgow signing (Dec. 2, 2017)
Other than those, basically everything has been RAFOed