Iorwerth's message is an item used in Regicide. After killing King Tyras, Lord Iorwerth gives the player this mystically sealed message to give to King Lathas. Before the player can deliver it, they are stopped by Arianwyn, who uses his own magic to open the letter and reveal Lathas's true intentions, destroying Camelot, to the player.
Your Majesty King Lathas
Your agent did well. The path is now open for the Dark
Lord to enter this realm. You will yet live to see Camelot
crushed under foot.