Odin was now so weak that he was dying. Not only because of the Twilight of the Gods but also because he was sitting on the Iron Throne for 23 centuries, not recuperating but draining his energy to power the shroud.
The spaceship shield was powered by its reactor. But since the control system was offline and Odin was unable to take over the control, he needed to use his own strength to power the shield to control the defense system. This additional energy need was taking a toll on him.
Even Odin himself had never thought that he would one day sit on such a throne and pay with his life to shelter those weaklings and ignorant humans.