I was pretty excited when Nightblood showed up at the end of Words of Radiance. I've read almost all of Brandon's books, and this was the first obvious crossover between different series. (The second, if you count Hoid as obvious.)
This leads me to wonder how different magic systems of the 'cosmere' are going to interact. The Szeth question in the header is kind of representative of that more general question, but the conversation doesn't need to be restricted to Szeth. The members of this forum seem to have sources of information beyond the books, so please enlighten a fan who doesn't.
From Warbreaker, it seems that when Nightblood is unsheathed, it will continuously drain BioChromatic Breaths from its wielder, and kill any wielder who doesn't have Breath. But there doesn't seem to be a steady source of Breaths on Roshar for Szeth to use.
Or maybe there is? Can Breath on Roshar be transferred from one person to another by saying the words (My life to yours, ...)? Maybe it's just never been tried?
Alternatively, could Nightblood be powered by Stormlight instead? Are Breath and Stormlight (and metals, and whatever powers Aeons, ...) really the same thing?
Cheers!