The personality and memories of the late Magic King that has been sealed within a powerful magic-sword. Kail picked up Sildonia as a reward for reaching the treasure room of the Magic King's Great Labyrinth, and fought as Kail's sword and knowledge in the original timeline. This prompts Kail to acquire the sword again in the new timeline in order to have Sildonia remain at his side. Acquiring the sword once more, Sildonia learns of Kail's memories as someone who jumped back in time, and decides to help Kail's quest to prepare for the Great Invasion.