The rewards of History Quests were on a whole different level than other more common quests, and this was even greater in Kaizen's current case, considering that the entire quest trail he completed directly involved the Spelloyal Family, who rule the Tretidian Kingdom, one of the largest Human Kingdoms in all of Midgard. Furthermore, the very fate of this kingdom has changed dramatically thanks to Kaizen's interference, and if not for him, a perhaps devastating fate awaited these lands.
King Steveren Spelloyal knew that he could not let something great like this pass without an equally great thank you, both for having been saved by Kaizen, and also for all that the Psyker had done for his family.
When Kaizen arrived in the throne room, which surprisingly was being restored very quickly by some mages, he felt anxious. Being called by the King after completing a mission was cliché, but the fact that he did not know what the rewards would be made him uneasy.