So as of RoW...
Szeth has been in jail for a year.
Szeth has a freaky black sword.
Unless they're real lenient in Urithiru prisons, Szeth was probably not allowed to keep his freaky black sword with him.
Therefore: a) where is Nightblood now? and 2) how likely is it that Zahel knows? and III) what is he going/planning to do? If he didn't do it already.