So by the end of OB, Szeth had said the Third Ideal of the Skybreakers and bonded a spren. My question is why would Szeth use Nightblood instead of summoning his shardbalde when fighting in the battle at the end? Seems like it would have been less of a risk rather than having Nightblood constantly draining stormlight and almost killing him. I assume it is because Szeth didn't consider summoning his spren because he hasn't summoned living shardblade before but I find it odd.
Also, will Szeth keep Nightblood and have his spren as shardblade? I know Nightblood is supposed to be more powerful than a shardblade but kinda seems like the risks outweigh the rewards when weilding it.