The Fellowship of the Ring by J.R.R Tolkien (Harper Collins 1991) pp. 234-36
One by one the company who are the Council of Elrond tell of how it is that they have come to Rivendell and as each listens to the other they begin to learn the truth of what Elrond says of how it is that they are sitting there on that October morning.
“You have come and are here met, in this very nick of time, by chance as it may seem. Yet it is not so. Believe rather that it is so ordered that we, who sit here, and none others, must now find counsel for the peril of the world.”

And so it is that Gloín is the first to give an account of why he is in Rivendell that day. A messenger of Sauron had come to the Kingdom under the Mountain seeking news of hobbits. For “one of these was known to you on a time”. That hobbit, of course, is Bilbo and the messenger seeks him because of the Ring. Although it is not stated explicitly it is clear as we read Gloín’s account that the messenger is a Ringwraith, one of the nine, the Nazgûl. His breath came “like the hiss of snakes” and all who stand near by shudder. Sauron wishes for his embassy to have a maximum impact and requires a herald who will be a cause of fear in all who hear him.

But if Sauron’s intention is to create fear what he achieves is to inspire resistance. The messenger’s mention of hobbits serves only to remind Dáin Ironfoot, the King under the Mountain, of his bond of obligation to Bilbo without whom he would never have gained his crown. And it serves also to remind him and the other chieftains of the dwarves of the alliance that fought the Battle of the Five Armies and the shelter and counsel that Thorin Oakenshield’s party received at Rivendell during their journey. For we should not assume that just because Gloín and his companions are present at the Council that this represents a normal state of affairs in which ambassadors go to and fro between the hidden valley and the lonely mountain. If there is an ambassador whose labour in making alliances between the free peoples of Middle-earth is bearing fruit on this day in Rivendell then it is Gandalf, the Grey Pilgrim, the one who encouraged Thorin to make his journey to Erebor and who, for some strange reason, had him take a hobbit with him. And it was Gandalf who brought together the men of Dale and Esgaroth, the elves of the Woodland Realm and the dwarves to defeat the orcs of the Misty Mountains. Gandalf has followed hunches, grasped at straws, and held onto fool’s hopes many times and for many years before this moment, many times before the decision is made that will be the outcome of this Council.

Sauron too has been a builder of alliances over many long years. He is gathering them together for the great war even as the Council deliberates. He knows that many of the peoples of Middle-earth are not natural allies for all Gandalf’s efforts. There has been little love between elf and dwarf through the ages, much suspicion and sometimes outright hostility and even war. The dwarves have fought many battles against orcs through the centuries but apart from the Battle of the Five Armies they have fought them alone and they have usually felt alone in the world. Sauron’s alliance building is usually a mixture of threat and gift and so it is with the dwarves. The threat is war and the gift is of two of the rings of power once held by dwarf lords, rings that greatly increased their wealth. What choice will the dwarves make in the war that is to come?
It was no accident that Elrond placed Frodo and Gloín together at the table top of highest honour at the feast the night before. Gloín, the companion of Thorin Oakenshield had to become acquainted with the heir of Bilbo, the Ringbearer. He had to be reminded bodily of the bond between dwarves and hobbits, with the family of Bilbo.
“You have done well to come,” Elrond says to Gloín after Gloín speaks of his fears. “You will hear today all that you need in order to understand the purposes of the Enemy. There is naught that you can do, other than to resist, with hope or without it. But you do not stand alone. You will learn that your trouble is but part of the trouble of all the western world.”

Interesting point about Dain: the gratitude of kings might be the most fantastical element in LotR.
By fantastical do you mean in this case, unbelievable? Surely in Tolkien’s world gratitude is an essential virtue for a king? Ingratitude always ends badly. One thinks of Thingol and Beren.
You’re right — I hadn’t even thought about ingratitude ending badly.