Demise rode his bird hard - just what the Loftwing could take. He did not want to lose his steed, too. He carried Girahim to his own bedchamber in the silver castle and laid him out in the bed. Demise was normally a god of endings, the bringer of necessary misfortunes to keep the cycle of the world going, but he knew some healing spells. Hylia had taught him how to access healing energies.
He ran his hands over Girahim, willing a golden glow over him. He did not know if this would work, if it would be too late.
He could sense that Fi was absent from the castle. He really needed her around. The swords were counterparts to one another. If Demise couldn't save Girahim, Fi probably could.