Initially, I had the impression that the honor spren bonding with an indiviual is what gave the radiants their power or at least magnified it. However, at the end, Syl expresses disgust with the shard blade and that she was happy that Dalinar got rid of it.
It also seems that the blades were used by the radiants in the flashbacks.
In addition, there is no metion of spren of any kind in the scenes that are from Szeth's POV.
My question is Syl actually related to Kal's increasing ability, or does she have another part to play?
I know this is a classic RAFO, but it will have me scratching my head while waiting for the next installment.