The epigraphs on the chapters of The Way of Kings Part 2 are of particular note, as they reveal some hints at the history of the Cosmere and the Shards of Adonalsium, as well as at the history and personality of their author. They set the stage for the conflict on Roshar: not only is this one world at stake, but the entire Cosmere might fall if the Shardholder of Odium, Rayse, gets what he wants.
The epigraphs are phrased as a letter, and are best read and understood all at once. For convenience in reading they are reproduced here. The number preceding each paragraph indicates the chapter number in which the epigraph appears.
 Full Text
“ Old friend, I hope this missive finds you well. Though, as you are now essentially immortal, I would guess that wellness on your part is something of a given. I realize that you are probably still angry. That is pleasant to know. Much as your perpetual health, I have come to rely upon your dissatisfaction with me. It is one of the cosmere's great constants, I should think.
Let me first assure you that the element is quite safe. I have found a good home for it. I protect its safety like I protect my own skin, you might say. You do not agree with my quest. I understand that, so much as it is possible to understand someone with whom I disagree so completely. Might I be quite frank? Before, you asked why I was so concerned. It is for the following reason: Ati was once a kind and generous man, and you saw what became of him. Rayse, on the other hand, was among the most loathsome, crafty, and dangerous individuals I had ever met. He holds the most frightening and terrible of all the Shards. Ponder on that for a time, you old reptile, and tell me if your insistence on nonintervention holds firm. Because I assure you, Rayse will not be similarly inhibited. One need only look at the aftermath of his brief visit to Sel to see proof of what I say. In case you have turned a blind eye to that disaster, know that Aona and Skai are both dead, and that which they held has been Splintered. Presumably to prevent anyone from rising up to challenge Rayse.
You have accused me of arrogance in my quest. You have accused me of perpetuating my grudge against Rayse and Bavadin. Both accusations are true. Neither point makes the things I have written to you untrue. I am being chased. Your friends of the Seventeenth Shard, I suspect. I believe they're still lost, following a false trail I left for them. They'll be happier that way. I doubt they have any inkling what to do with me should they actually catch me. If anything I have said makes a glimmer of sense to you, I trust that you'll call them off. Or maybe you could astound me and ask them to do something productive for once. For I have never been dedicated to a more important purpose, and the very pillars of the sky will shake with the results of our war here. I ask again. Support me. Do not stand aside and let disaster consume more lives. I've never begged you for something before, old friend.
I do so now.”— The Letter
It is confirmed that we "may have read that Hoid has specific beef with Rayse." As for only the Letter tells about Hoid having a grudge against Rayse this can be seen as an acknowledgement that Hoid wrote the Letter.