It was the last day of the ultimatum that the berserkers had given to the IGT Federation. They had demanded the Federation to send one Voyager to Kermurkheim and had threatened that if they failed to do so, all of the hostages would be killed as soon as the given time ended.
After making the employees of IGT Fed to work for them for four years, the berserkers knew that they were all compassionate, which was their weakness. Thus, they were expecting the IGT Fed to comply with their demands. They thought that they were fools who would fall right into their traps.
As it was the last day, the King had asked the berserkers who were trained to fly to gather up in a large hall which served the purpose of the throne hall. In that hall, Krorr Marru had kept the throne made out of bones of the unfortunate beings.