Hi there, I have a little theory I thought of while rereading Oathbringer. In chapter 67 when Shallan sees Hoid for the first time in Kholinar. He’s telling the story of the moons when he is started by something in his pack, he later looks for Shallan in the crowd, and at the end of the chapter she notices a jar that is full of a black substance however the side facing her is white. The substance is presumably sand from Taladin. My theory is that the sand fed of Shallan’s stormlight recharging it, which is why Hoid was surprised (I would assume he knows the sand can recharge with stormlight, however I’m not sure that he would know there was a surgbinder in the crowd) and made him seek Shallan out in the crowd.